AS 1668.2—2012
(Incorporating Amendment Nos 1 and 2)
AS 1668.2—2012
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The use of ventilation and
airconditioning in buildings
Part 2: Mechanical ventilation in
buildings
This Australian Standard® was prepared by Committee ME-062, Ventilation and Air
conditioning. It was approved on behalf of the Council of Standards Australia on 12 October
2012.
This Standard was published on 20 November 2012.
The following are represented on Committee ME-062:
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Air Conditioning and Mechanical Contractors Association
Australasian Fire and Emergency Service Authorities Council
Australian Building Codes Board
Australian Industry Group
Australian Institute of Refrigeration Air Conditioning and Heating
Chartered Institute of Building Services Engineers
Climate Control Companies Association
Consumer Electronic Suppliers Association
Department of Health and Human Services, Tasmania
Engineers Australia
Facility Management Association of Australia
Fire Protection Association Australia
Institute of Refrigeration Heating and Air Conditioning Engineers of New Zealand
Plastics and Chemical Industries Association
Plumbing Industry Commission
Property Council of Australia
This Standard was issued in draft form for comment as DR AS 1668.2.
Standards Australia wishes to acknowledge the participation of the expert individuals that
contributed to the development of this Standard through their representation on the
Committee and through the public comment period.
Keeping Standards up-to-date
Australian Standards® are living documents that reflect progress in science, technology and
systems. To maintain their currency, all Standards are periodically reviewed, and new editions
are published. Between editions, amendments may be issued.
Standards may also be withdrawn. It is important that readers assure themselves they are
using a current Standard, which should include any amendments that may have been
published since the Standard was published.
Detailed information about Australian Standards, drafts, amendments and new projects can
be found by visiting www.standards.org.au
Standards Australia welcomes suggestions for improvements, and encourages readers to
notify us immediately of any apparent inaccuracies or ambiguities. Contact us via email at
mail@standards.org.au, or write to Standards Australia, GPO Box 476, Sydney, NSW 2001.
AS 1668.2—2012
(Incorporating Amendment Nos 1 and 2)
Australian Standard®
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The use of ventilation and
airconditioning in buildings
Part 2: Mechanical ventilation in
buildings
First published as AS 1668.2—1976.
Fifth edition 2012.
Reissued incorporating Amendment No. 1 (October 2013).
Reissued incorporating Amendment No. 2 (December 2016).
COPYRIGHT
© Standards Australia Limited
All rights are reserved. No part of this work may be reproduced or copied in any form or by
any means, electronic or mechanical, including photocopying, without the written
permission of the publisher, unless otherwise permitted under the Copyright Act 1968.
Published by SAI Global Limited under licence from Standards Australia Limited, GPO Box
476, Sydney, NSW 2001, Australia
ISBN 978 1 74342 298 4
AS 1668.2—2012
2
PREFACE
This Standard was prepared by Standards Australia Committee ME-062, Ventilation and Air
Conditioning, to supersede AS 1668.2—2002, The use of ventilation and airconditioning in
buildings, Part 2: Ventilation design for indoor air contaminant control (excluding
requirements for the health aspects of tobacco smoke exposure).
This Standard incorporates Amendment No. 1 (October 2013) and Amendment No. 2
(December 2016). The changes required by the Amendment are indicated in the text by a
marginal bar and amendment number against the clause, note, table, figure or part thereof
affected.
The objective of this Standard is to provide users with minimum design parameters and
guidelines for determining ventilation rates for general application in buildings.
This Standard has been prepared for reference in the National Construction Code (NCC).
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In accordance with the philosophy of adopting a complementary approach to building
regulations, the main technical change to the Standard is the update of AS 1668.2—2002 to
reflect current technology and approaches for ventilation as well as the relocation of natural
ventilation content to the new Standard AS 1668.4, The use of ventilation and
airconditioning in buildings, Part 4: Natural ventilation of buildings. Within that approach,
the structure of the Standard has been revised to include a new prescribed approach to car
park ventilation and the use of ‘borrowed’ ventilation for multi-use compartments. The
main technical changes are summarized as follows:
(a)
A simplified methodology for multi-use enclosures using mass flow proportioning.
(b)
Minimum outdoor airflow rates have been normalized in line with the removal of all
references to ‘environmental tobacco smoke’.
(c)
Requirements for natural ventilation systems have been excluded.
(d)
Outdoor airflow rate calculations have been presented using the concept of ‘effective
outdoor airflow’.
(e)
Requirements for kitchen exhaust hood design have been rationalized and expanded
to cover additional scenarios and reflect recent changes in hood technology and
application.
(f)
Equations used for calculation of total airflow rates in car parks have been presented
as ‘simple’ and ‘detailed’ procedures.
(g)
Alternative air distribution methods for car parks have been included.
In the preparation of this Standard, consideration was given to a number of international
and national Standards, design guides, technical papers, manuals and other publications.
The terms ‘normative’ and ‘informative’ have been used in this Standard to define the
application of the appendix to which they apply. A ‘normative’ appendix is an integral part
of a Standard, whereas an ‘informative’ appendix is only for information and guidance.
Statements expressed in mandatory terms in notes to Tables are deemed to be requirements
of this Standard.
This Standard incorporates a Commentary on some clauses. The Commentary is set
directly following the relevant clause and is designated by ‘C’ preceding the clause
number and printed in italics in a panel, The Commentary is for information only and
does not need to be followed for compliance with the Standard.
3
AS 1668.2—2012
CONTENTS
Page
FOREWORD .............................................................................................................................. 5
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SECTION 1 SCOPE AND GENERAL
1.1 SCOPE ......................................................................................................................... 6
1.2 APPLICATION ........................................................................................................... 6
1.3 NORMATIVE REFERENCES .................................................................................... 8
1.4 DEFINITIONS............................................................................................................. 9
1.5 COMBINATION VENTILATION SYSTEMS .......................................................... 13
1.6 RESIDUAL VENTILATION .................................................................................... 13
1.7 SYSTEM OPERATION ............................................................................................ 13
SECTION 2 MECHANICAL VENTILATION—SUPPLY SYSTEMS
2.1 SCOPE OF SECTION ............................................................................................... 14
2.2 NOTATION ............................................................................................................... 15
2.3 OUTDOOR AIR INTAKES....................................................................................... 16
2.4 TUNDISHES AND FLOOR WASTES ...................................................................... 16
2.5 FILTRATION ............................................................................................................ 16
2.6 PROHIBITION OF RECYCLE AIR .......................................................................... 17
2.7 OUTDOOR AIR MIXING AND DISTRIBUTION ................................................... 18
2.8 OUTDOOR AIRFLOW RATES ................................................................................ 18
2.9 OUTDOOR AIRFLOW ADJUSTMENT ................................................................... 22
SECTION 3 MECHANICAL VENTILATION—EXHAUST SYSTEMS
3.1 SCOPE OF SECTION ............................................................................................... 27
3.2 EXHAUST VENTILATION...................................................................................... 29
3.3 LOCAL EXHAUST ................................................................................................... 29
3.4 KITCHEN EXHAUST HOODS ................................................................................ 31
3.5 KITCHEN EXHAUST HOOD AIRFLOW—PRESCRIPTIVE PROCEDURE ......... 34
3.6 VENTILATED CEILINGS AND PROPRIETARY KITCHEN EXHAUST
EQUIPMENT (HOOD TYPES 5 AND 7) ................................................................. 35
3.7 AIR FROM ENCLOSURES HAVING EXHAUST AIR REQUIREMENTS ............ 35
3.8 REPLENISHMENT OF EXHAUST AIR .................................................................. 35
3.9 COMBINATION OF EXHAUST SYSTEMS ............................................................ 37
3.10 AIR DISCHARGES ................................................................................................... 38
SECTION 4 VENTILATION OF ENCLOSURES USED BY VEHICLES WITH
COMBUSTION ENGINES
4.1 SCOPE OF SECTION ............................................................................................... 42
4.2 APPLICATION OF SECTION .................................................................................. 44
4.3 NOTATION ............................................................................................................... 44
4.4 CAR PARKS ............................................................................................................. 46
4.5 ENCLOSURES OTHER THAN CAR PARKS .......................................................... 49
4.6 QUEUING AREAS ................................................................................................... 51
4.7 AIR PRESSURE ........................................................................................................ 52
4.8 MAKE-UP OF EXHAUST AIR ................................................................................ 52
4.9 EXHAUST AIR DISCHARGE .................................................................................. 52
4.10 COMBINATION SYSTEMS ..................................................................................... 52
4.11 VENTILATION CONTROL ..................................................................................... 53
4.12 MONITORING OF ATMOSPHERIC CONTAMINANTS........................................ 54
AS 1668.2—2012
4
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SECTION 5 MECHANICAL VENTILATION OF ENCLOSURES USED FOR
PARTICULAR HEALTH CARE FUNCTIONS
5.1 SCOPE OF SECTION ............................................................................................... 56
5.2 APPLICATION OF SECTION .................................................................................. 56
5.3 OPERATING ROOMS .............................................................................................. 57
5.4 STERILE STORE AND SET-UP ROOMS ................................................................ 58
5.5 INFECTIOUS ISOLATION ROOMS ........................................................................ 58
5.6 PROTECTIVE ISOLATION ROOMS....................................................................... 59
5.7 POST ANAESTHETIC CARE UNIT (PACU) (Recovery Stage 1) ........................... 59
5.8 AUTOPSY ROOMS .................................................................................................. 60
5.9 DIRTY UTILITY ROOMS ........................................................................................ 60
APPENDICES
A
MINIMUM EFFECTIVE OUTDOOR AIRFLOW REQUIREMENTS BASED ON
OCCUPANCY ........................................................................................................... 61
B
MINIMUM MECHANICAL EXHAUST AIR REQUIREMENTS BASED ON USE
OF ENCLOSURE ...................................................................................................... 68
C
OUTDOOR AIR CONTAMINANT LEVELS ........................................................... 71
D
PRINCIPLES OF VENTILATION AIRFLOW ANALYSIS ..................................... 72
E
KITCHEN EXHAUST HOODS ................................................................................ 84
F
PERFORMANCE-ORIENTED APPROACHES TO MECHANICAL VENTILATION
SYSTEM DESIGN (INCLUDING SYSTEM COMPONENT SELECTION) ............ 95
G
RATIONALE FOR LAG OR LEAD TIME FOR TRANSIENT OCCUPANCY ..... 100
H
COMMENTARY ON CARBON MONOXIDE EXPOSURE IN OCCUPATIONAL
ENVIRONMENTS .................................................................................................. 102
I
EXAMPLES OF LAYOUTS OF CAR PARK VENTILATION .............................. 104
J
BASIS OF AIRFLOW RATES FORMULAE FOR CAR PARKS ........................... 108
K
BASIS FOR LENGTH OF VEHICLE QUEUE IN CAR PARKS............................ 111
L
DERIVATION OF AIRFLOW RATES FOR QUEUING AREAS IN CAR PARKS
................................................................................................................................. 112
M
AUTOMATIC MONITORING SYSTEMS FOR CAR PARKS—MARKING,
COMMISSIONING, RELIABILITY AND RECORDS ........................................... 113
N
PERFORMANCE APPLICATION TO CAR PARK VENTILATION .................... 114
O
LOCAL EXHAUST VENTILATION REFERENCES ............................................ 116
BIBLIOGRAPHY ................................................................................................................... 117
5
AS 1668.2—2012
FOREWORD
This Standard sets permissible ventilation rates having consideration to health and
ventilation amenity. The specified ventilation rates are intended to maintain general
contaminants (e.g. body odours, volatile organic compounds and the like) at concentrations
below exposures that have the potential to cause adverse health effects to a majority of
occupants.
Requirements for the design of natural ventilation systems have been excluded from this
document and have been relocated in the new Standard AS 1668.4, The use of ventilation
and airconditioning in buildings, Part 4: Natural ventilation of buildings. Where possible,
this Standard is prescriptive based and calculations are presented as ‘simple’ and ‘detailed’
procedures.
Ventilation rates specified may not ensure that specific contaminants (e.g. fumes from
unflued gas-fired devices and other fumes) are maintained at concentrations below
exposures that have the potential to cause adverse health effects. When specific
contaminants are present, alternative or additional control measures, other than dilution,
may need to be implemented to achieve an equivalent level of health and amenity.
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A simple method of calculating ventilation rates to meet the requirements is included. The
method is based on a default multiple enclosure factor with a design check step to verify
that the underlying assumptions are incorporated.
The sections on kitchen exhaust and car park ventilation have been revised in line with the
general performance philosophy and updated to reflect ventilation systems available to the
market.
It is recognized that this Standard is likely to be used for occupational health and
community health purposes; thus, its provisions have been designed, to the extent possible,
to community health criteria promulgated by peak health bodies. Implicit in this recognition
is the possibility that the provisions of the Standard may, at least in part, be excessively
conservative when applied in an occupational health context. The Standard has used a
two-part approach to the setting of ventilation rates for health purposes, which comprises a
general approach and a more specific approach where particular information is available.
The principal health basis of the ventilation requirements of this Standard are based on
enclosures in which smoking does not occur. This represents acceptance that ventilation
rates long in use in Australia for health purposes remain valid in circumstances where
available information does not allow a more specific or scientific approach. Where there is
reasonably predictable pollutant generation information and an authoritative community
health exposure limit, then that information has been used to set ventilation rates.
AS 1668.2—2012
6
STANDARDS AUSTRALIA
Australian Standard
The use of ventilation and airconditioning in buildings
Part 2: Mechanical ventilation in buildings
SECTI ON
1
SCOPE
AND
GENERAL
1.1 SCOPE
This Standard sets out design requirements for mechanical air-handling systems that
ventilate buildings and car parks (see Note 1), and requirements for ventilation based on the
need to control odours, particulates and specific gases (e.g. CO, NOx , CO2 , VOCs).
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This Standard does not include requirements—
(a)
associated with comfort (e.g. temperature, humidity, air movement or noise);
(b)
for the maintenance of ventilation and air-handling systems;
(c)
for natural ventilation systems, apart from natural make-up or relief to mechanical
systems (see Note 1);
(d)
for the elimination of condensation;
(e)
for the provision of ventilation to ensure the safe operation of gas appliances; and
(f)
for safety aspects associated with fire and smoke.
NOTES:
1 Requirements for natural ventilation of buildings (including car parks) are covered by
AS 1668.4 and the NCC.
2 Road tunnels and other non-building related applications are outside the scope of this
Standard.
3 Fire and smoke control aspects of air-handling systems are covered in AS/NZS 1668.1 and
AS 1668.3.
4 Requirements for system design in respect of microbial control are given in AS/NZS 3666.1.
5 Air-handling systems should be designed, constructed and installed so that their use does not
give rise to a noise or vibration nuisance. For guidance on noise and vibration control, see
AS 1055.1 and AS 2107.
6 Information on thermal comfort conditions is given in ISO 7730 and ASHRAE 55.
7 This Standard covers the design of ventilation systems for industrial processes.
8 Requirements for ventilation in relation to the safe operation of gas appliances are covered in
AS/NZS 5601.1.
1.2 APPLICATION
1.2.1 General
This Standard is intended for use by regulatory authorities, building services designers,
architects, equipment manufacturers and suppliers, installers, managers, owners and
operating staff responsible for designing and administering, air-handling systems.
C1.2.1 It is intended that this Standard be applied to new buildings at the design stage.
Its application to some existing buildings may be inappropriate and, in such instances,
alternative designs and solutions may be necessary.
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AS 1668.2—2012
1.2.2 Mechanical ventilation systems selection
The following applies to the selection of mechanical ventilation systems:
(a)
For processes or enclosures listed in Appendix A and similar enclosures, supply
ventilation complying with Section 2 shall be provided. Alternatively, mechanical
exhaust air ventilation together with appropriate make-up air may be provided in lieu
of supply ventilation, provided any adjacent enclosure of different use, as listed in
Appendix B, is maintained at a lower pressure at all times.
(b)
For processes or enclosures listed in Appendix B and similar enclosures, general
exhaust complying with Section 3 shall be provided.
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Alternatively, the following may be provided:
(i)
Local exhaust air systems may be used in lieu of part of or whole of the general
exhaust ventilation, provided it can be demonstrated they are as effective in the
removal of effluent as the required general exhaust system.
(ii)
For enclosures for which discharges are not deemed objectionable (see
Table 3.3) mechanical supply air ventilation together with permanently open
natural relief air openings may be provided in lieu of general exhaust
ventilation, provided any adjacent enclosure of different use is maintained at a
higher pressure at all times. In such cases, relief air openings shall comply with
Clause 3.10.2.
(c)
For processes or enclosures subject to Type A or Type B effluent, as described in
Clause 3.3, local exhaust complying with Section 3 shall be provided.
(d)
For enclosures accommodating automotive vehicles with combustion engines,
mechanical supply or mechanical exhaust or both shall be provided as necessary to
meet the requirements of Section 4.
(e)
For enclosures used for particular health care functions, ventilation systems shall
comply with Section 5.
NOTE: Guidance on the selection of ventilation systems is given in Figure 1.1.
C1.2.2 Enclosures that may need mechanical ventilation are as follows:
(a) Enclosures that are not adequately naturally ventilated.
(b) Industrial or other premises where it is essential to remove dust, toxic or noxious
contaminants at, or near, their source (see Section 3).
(c) Health care facilities where it is needed to control infection (e.g. operating
theatres), or to control cross-infection [e.g. between isolation wards (see
Section 5)].
(d) Spaces where unfavourable external environmental conditions exist (e.g. excessive
noise, pollution or dust).
(e) Enclosed car parks, driveways and similar spaces where it is necessary to dilute
hazardous gases and fumes (see Section 4).
(f) Spaces with a high density of continuing occupancy expected (e.g. auditoriums or
clubs).
(g) Spaces where high heat and vapour generation is likely [e.g. large commercial
kitchens and laundries (see Section 3)].
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AS 1668.2—2012
8
STA R T
(fo r e a c h e n c l o s u r e)
D o e s th e e n c l o s u r e
require supply air
dilu ti o n ve ntil ati o n?
Ye s
S ECT I O N
2
FIG U R E 2.1
No
I s th e t y p e of e n c l o s u r e
L i s te d i n Ta b l e B1, A p p e n di x B?
Ye s
S ECT I O N
3
FIG U R E 3 .1
No
A r e c o m b u s ti o n
e n g i n e s o p e r ate d
i n th e e n c l o s u r e?
Ye s
S ECT I O N
4
FIG U R E 4.1
Ye s
S ECT I O N
5
FIG U R E 5.1
No
I s th e e n c l o s u r e u s e d fo r
a p a r ti c ul a r h e ath c a r e
f u n c ti o n, a s p e r C l a u s e 5. 2
(a), ( b), (c), (d ), (e), (f ) o r (g)
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No
EN D
FIGURE 1.1 FLOW CHART FOR THE SELECTION OF VENTILATION SYSTEMS
1.3 NORMATIVE REFERENCES
The following documents are the normative documents referenced in this Standard:
AS
1324
1324.1
1324.2
Air filters for use in general ventilation and airconditioning
Part 1: Application, performance and construction
Part 2: Methods of test
1530
1530.1
Methods for fire tests on building materials, components and structures
Part 1: Combustibility test for materials
1735
1735.1
Lifts, escalators, and moving walks
Part 1: General requirements
2676
2676.2
Guide to the installation and maintenance, testing and replacement of
secondary batteries in buildings
Part 2: Sealed cells
3772
Pre-engineered fire protection systems for cooking equipment
4260
High efficiency particulate air (HEPA) filters—Classification, construction and
performance
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9
AS/NZS
1668
1668.1
The use of mechanical ventilation and airconditioning in buildings
Part 1: Fire and smoke control in multi-compartment buildings
1677
1677.2
Refrigerating systems
Part 2: Safety requirements for fixed applications
AS 1668.2—2012
NCC
National Construction Code
1.4 DEFINITIONS
For the purpose of this Standard, the definitions given in the NCC and those below apply.
NOTE: A representation of air-handling terms is shown in Figure 1.2.
1.4.1 Airflow rate
The volumetric flow rate of air derived from the mass flow rate by dividing it by the
density, normalized to 1.2 kg/m3 (1.2 g/L).
NOTE: For buildings located at an altitude substantially differing from sea level, specified
airflow rates should be adjusted.
1.4.2 Air-handling plant
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A component part of an air-handling system that includes equipment that provides air
movement, as well as equipment for the purpose of controlling the direction, rate of airflow,
division of airflow and condition of air.
1.4.3 Air-handling system
A system for the purpose of directing air in a controlled manner to or from specific
enclosures or parts of enclosures by means of air-handling plant, ducts, plenums,
air-distribution devices and automatic controls, which include industrial ventilation for the
removal of Type A effluents [see Clause 3.3.1(a)].
1.4.4 Airlock
A room or compartment provided to disconnect a sanitary compartment or other enclosure
from another room or space in the building.
1.4.5 Air outlet
Any opening through which air is delivered to an enclosure by an air-handling system of a
building.
1.4.6 Competent person
A person who has had appropriate training or practical experience (or both) to provide safe
and satisfactory performance.
1.4.7 Duct
A component part of an air-handling system that is intended for the passage of air from one
part of an air-handling system to another (see also definition of ‘plenum’).
1.4.8 Effective outdoor airflow
The sum of introduced outdoor air, residual effective outdoor air recycled from the
enclosure(s), air-cleaning device effective outdoor air and transferred effective outdoor air.
1.4.9 Enclosure
An individual room, space or part thereof.
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AS 1668.2—2012
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1.4.10 Exhaust air
Air, other than return air, removed from an enclosure by mechanical means and discharged
to atmosphere.
1.4.11 Exhaust air intake
Any opening through which air is extracted from an enclosure by an air-handling system.
1.4.12 Exhaust discharge
An outlet from an air-handling system discharging to atmosphere.
1.4.13 Exposure limit (EL)
1
For occupational exposure, values designated by NOHSC.
2
For community exposure, values based on standards and goals set by NHMRC and
NEPC.
NOTE: NOHSC (National Occupational Health and Safety Commission; NHMRC (National
Health and Medical Research Council); NEPC (National Environment Protection Council).
1.4.14 General exhaust ventilation
Ventilation of an enclosure by the extraction of air from that enclosure, thereby allowing
contaminants to be diluted by supply air or make-up air, the mixture being collected at
exhaust air intakes and discharged outside the building (see Figure 1.2).
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1.4.15 General contaminants
Contaminants that are generated by occupants, the building or devices (e.g. body odours,
volatile organic compounds, and the like) and found within most buildings.
1.4.16 Grease removal device
A device that removes grease and lint from the airstream.
1.4.17 Hood
A component part of a local exhaust system intended for collecting effluent.
1.4.18 Indoor air
Air inside the enclosure under consideration (see Figure 1.2).
1.4.19 Infiltration air
Air (other than supply air and make-up air) that enters an enclosure or an air-handling
system in an uncontrolled manner (see Figure 1.2).
1.4.20 Introduced outdoor airflow
Air introduced to an air-handling system via an outdoor air intake.
1.4.21 Leakage air
Air (other than exhaust air return air and relief air) that escapes from an air-handling system
in an uncontrolled manner (see Figure 1.2).
1.4.22 Local exhaust
Extraction of objectionable or hazardous effluent close to the source and discharging to
atmosphere (see Figure 1.2).
1.4.23 Make-up air
Air that enters an enclosure or an air-handling system in a controlled manner but not by
direct mechanical means (see Figure 1.2).
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AS 1668.2—2012
1.4.24 May
Indicates the existence of an option.
1.4.25 Occupied zone
The region within an occupied space between planes 75 mm and 1800 mm above the floor
and more than 600 mm from the walls or fixed air-handling equipment.
1.4.26 Outdoor air
Air outside the building (see Figure 1.2).
1.4.27 Outdoor air intake
Any opening through which outdoor air is admitted to an air-handling system of a building.
1.4.28 Plant room
A room that contains any items of plant or machinery (see Clause 2.3.2).
1.4.29 Plenum
An air compartment or chamber intended for the passage of air, to which one or more ducts
may be connected and which forms part of an air-handling system.
1.4.30 Privacy lock
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A room or compartment whose function is to provide a visual or acoustic barrier, and not
provided to disconnect a sanitary compartment from another room or space through which
persons pass to enter the sanitary compartment.
1.4.31 Local air
Enclosure air that passes through a local air-cleaning unit and returns to the same enclosure.
1.4.32 Recycle air
That portion of indoor air removed by mechanical means from enclosures as return air and
returned as part of the supply air (see Figure 1.2).
1.4.33 Relief air
Air that flows from an enclosure in a controlled manner by other than direct mechanical
means (see Figure 1.2).
1.4.34 Required
Required by Standard or building regulation.
NOTE: Building owners and managers, fire insurance underwriters and other bodies may have
requirements in excess of those required by this Standard.
1.4.35 Residual effective outdoor airflow
A proportion of effective outdoor airflow that is in excess to the requirements of an
enclosure that is recycled back to the air-handling system.
1.4.36 Return air
Air removed from an enclosure by mechanical means.
NOTE: All of the return air may be expelled as spill air, or all or part of it may be recycled
(see Figure 1.2).
1.4.37 Shall
Indicates that a statement is mandatory.
1.4.38 Should
Indicates a recommendation.
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AS 1668.2—2012
12
1.4.39 Specific contaminants
Contaminants that are generated by occupants, the building or devices other than those
generally found within most buildings (e.g. fumes from unflued gas devices and other
fumes).
1.4.40 Spill air
That portion of return air that is not recycled (see Figure 1.2).
1.4.41 Supply air
Air introduced into an enclosure by mechanical means (see Figure 1.2).
1.4.42 Transfer air
Air that transfers between enclosures in an uncontrolled but predictable manner.
NOTE: Transfer air may be included into the calculations of effective outdoor airflow rate
(see Appendix D).
General
ex h a u s t
Lo c a l
ex h a u s t
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Relief air
( En c l o s u r e C)
M a ke - u p a i r
Tr a n s fe r a i r
( En c l o s u r e B)
C e ntr a l a i r
cleaning unit
( En c l o s u r e A )
O u td o o r a i r
Supply air
Recirculating
air
Indoor air
Lo c a l a i r
cleaning unit
R e c yc l e a i r
R e tu r n a i r
S p ill a i r
Relief air
Inf il tr ati o n a i r
Leakage air
FIGURE 1.2 REPRESENTATION OF AIR-HANDLING TERMS
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AS 1668.2—2012
1.5 COMBINATION VENTILATION SYSTEMS
Mechanical ventilation systems serving enclosures or parts of enclosures shall be arranged
so that their operation does not interfere with any natural ventilation systems serving
remaining parts of the enclosure or other enclosures. An enclosure that is only provided
with devices for the improvement of air movement within that enclosure shall be considered
as being naturally ventilated.
Ventilation systems may be combined to meet the requirements of this Standard. Possible
combinations include the following:
(a)
Mechanical supply with mechanical exhaust.
(b)
Mechanical supply with natural relief.
(c)
Natural make-up air with mechanical exhaust.
1.6 RESIDUAL VENTILATION
Residual ventilation (i.e. transfer air) may be used for areas of low or transient occupancy
such as corridors or similar. Residual ventilation may be incorporated into the calculations
of effective outdoor airflow rate.
A2
NOTE: For determination of residual effective outdoor airflows, see Paragraph D4, Appendix D.
1.7 SYSTEM OPERATION
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Ventilation systems shall be designed to be operable to suit the building occupancy.
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 Standards Australia
AS 1668.2—2012
14
SECTI ON
2
MECHANICAL VENTI LATION—
SUPPL Y SYSTEMS
2.1 SCOPE OF SECTION
This Section sets out requirements for outdoor air supply.
NOTES:
1 A flow chart on the application of this Section is shown in Figure 2.1.
2 For guidance on a performance-oriented approach to mechanical ventilation design, see
Appendix F.
S ECT I O N
2
Ca l c ul ate o c c u p a n cy fo r e a c h e n c l o s u r e
i n a c c o r d a n c e wi th Cl a u s e 2. 2. 2
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Ca l c ul ate m i ni m u m ef fe c tive o u td o o r a i r f l ow r ate
(s e e Fi g u r e 2. 2 fo r p r o c e d u r e)
If te m p e r atu r e of e n c l o s u r e m ay exc e e d 27°C u n d e r n o r m a l
conditions, modif y outdoor air flow in accordance with Clause 2.9.1
If e n c l o s u r e h a s va r i a b l e o r tr a n s i e nt o c c u p a n cy, o u td o o r a i r f l ow
m ay b e m o di f i e d i n a c c o r d a n c e wi th Cl a u s e 2.9. 2 o r 2.9. 3
A sys te m wi th va r i a b l e a i r vo l u m e to c o m p l y wi th Cl a u s e 2. 8.6
M a ke - u p a i r to c o m p l y wi th Cl a u s e 2. 8.7
O u td o o r a i r i nt a ke s to c o m p l y wi th Cl a u s e 2. 3
Fil te r s to b e p r ovi d e d i n a c c o r d a n c e wi th Cl a u s e 2. 5
R e cyc l e a i r p r o hib i te d f r o m li s te d e n c l o s u r e u nl e s s
tr e ate d i n a n a p p r ove d m a n n e r (s e e Cl a u s e 2.6)
O u td o o r a i r to b e r e a s o n a b l y u ni fo r ml y
di s tr ib u te d (s e e Cl a u s e 2.7 )
EN D
FIGURE 2.1 FLOW CHART ON THE APPLICATION OF SECTION 2
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 Standards Australia
15
AS 1668.2—2012
2.2 NOTATION
2.2.1 Symbols
The following symbols are used in this Section:
A
A2
= the area of the enclosure, in square metres
‘text deleted’
M
= multiple enclosure factor
n
= the occupancy for the enclosure served, as defined in Clause 2.2.2
N
= the occupancy, for all enclosures served by the air-handling system in accordance
with Clause 2.2.2
Qf = the flow rate of introduced outdoor air to the system, in litres per second
Qr = the flow rate of return air drawn from all enclosures served by an air-handling
system to be used as recycle air, in litres per second
Qs = the flow rate of supply air to all enclosures served by an air-handling system, in
litres per second
A2
qf
= the minimum effective outdoor airflow rate given in Appendix A, in litres per
second per metre squared of the floor area or litres per second per person
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qmin = the minimum effective outdoor airflow rate
qs
= the flow rate of supply air to the enclosure, in litres per second
R
= the ratio of the sum of required effective outdoor airflow rates for all enclosures
served to the total supply air for all enclosures served
rc
= the highest ratio, for any of the enclosures served, of effective outdoor airflow
required by Clause 2.8.5 to the corresponding supply air
2.2.2 Occupancy
The occupancy (n) of an enclosure shall be the greater of—
(a)
the maximum number of occupants present in the enclosure for any period exceeding
30 min; or
(b)
one-third of the maximum number of occupants present in the enclosure at any time.
Where the occupants of a group of enclosures, served by a single air-handling system, move
between those enclosures, it is not necessary to treat the total occupancy as the sum of the
maximum occupancies of each enclosure (n), rather, the distribution of occupants that
gives the highest required outdoor airflow rate shall be used (N).
The occupancy of the building is subject to building regulation. It shall be nominated for
the purposes of ventilation system design.
NOTE: In the absence of other information, the number of occupants should be not less than that
estimated on the basis of floor area per person. Maximum occupant density is given in
Appendix A.
C2.2.2 The occupancy values given in Appendix A are conservative and it is
recommended that actual values be nominated for design purposes. In some cases, the
occupancies used for the purposes of determination of outdoor airflow rates may differ
in aggregate for a given floor from those used for egress provisions in the NCC. This
can arise as a result of the use of the maximum occupancy for each area with no
account taken of movement of people from one area to another at different times during
the period of occupancy. An example would be a conference room used substantially by
the occupants of adjacent areas on the same floor.
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 Standards Australia
AS 1668.2—2012
16
2.3 OUTDOOR AIR INTAKES
2.3.1 Location
Intakes for outdoor air shall be located and arranged so that under all conditions of normal
operation—
(a)
contamination from air exhausts, cooling tower discharges, gas flues, work processes
and other sources of pollution do not reduce the quality of outdoor air entering the
intake to a level significantly below that of outdoor air in the locality, except where
outdoor air entering the intake is treated to achieve the same effect; and
(b)
the effects of wind, adjacent structures and other factors do not cause the flow rate of
outdoor air to be reduced below the minimum requirements of this Section.
C2.3.1 This Standard assumes that the outdoor air is generally acceptable for the
purposes of dilution ventilation. Where it has been established that the outdoor air is
not acceptable, pre-treatment of the outdoor air may be needed.
For guidance on acceptable contaminant concentrations in outdoor areas, see
Appendix C.
The 2009 ASHRAE Handbook—Fundamentals addresses airflow around buildings,
dispersion of building exhaust gases and design to minimize re-entry. Particularly
critical cases may warrant wind tunnel testing of models. Attention is drawn to
Clause 3.10 on the location of discharges.
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Gas flues are covered by AS 5601.1.
2.3.2 Passage of air
Outdoor air shall pass to the air-handling plant directly through a duct, plenum or plant
room connected to the intake.
Enclosures used for storage of equipment, plant or materials likely to contaminate the air
shall not be used as plenums. A plant room housing equipment or materials that do not
contaminate the air may act as a plenum.
2.4 TUNDISHES AND FLOOR WASTES
A duct or plenum shall not contain a tundish or floor waste that is not permanently charged.
NOTES:
1 Designing systems for charging by condensate only is not appropriate.
2 The installation of tundishes and floor wastes will need to comply with AS/NZS 3500.2.
2.5 FILTRATION
Any individual mechanical supply air ventilation system incorporating heating/cooling coils
or humidifiers, or both, shall incorporate an air filter rated to AS 1324.1 and in accordance
with Table 2.1. Such filters shall be positioned before supply air fans and any coils or
humidifiers and both the outdoor and recycle air shall be filtered as applicable.
NOTE: This requirement does not preclude the use of additional filters in other parts of the airhandling system.
Safe and convenient access for maintenance shall be provided to all filter installations.
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 Standards Australia
17
AS 1668.2—2012
C2.5 Filters can assist in the following:
(a) The removal of particulate contaminants from the air.
(b) The reduction of energy consumption through the reduction of dirt build-up on heat
transfer equipment.
(c) The maintenance of design airflows and aerodynamic performance of system
through the reduction of dirt build-up.
(d) The maintenance of the accurate response of control system components.
(e) The prevention of the malfunction of fire control equipment due to dust build-up
reducing the ability of a system to respond to a fire event.
TABLE 2.1
MINIMUM FILTER RATING
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System characteristics
Minimum filter rating
(see AS 1324.1)
1000 L/s ducted
G4
1000 L/s non-ducted
G4
<1000 L/s ducted
G2
<1000 L/s non-ducted
NR
Evaporative coolers
NR
LEGEND:
NR = no requirement
2.6 PROHIBITION OF RECYCLE AIR
Similar occupancies may be served by common recirculation systems. Except where the
recycle air is treated in an acceptable manner, air-handling systems serving more than one
enclosure shall not recycle air to dissimilar occupancies from any of the following
enclosures:
(a)
Any enclosure listed in Appendix B.
(b)
Any enclosure of the following types:
(i)
Equipment and store enclosures holding materials generating odours or noxious
gases.
(ii)
Animal enclosures, pet shops, veterinary centres, kennels.
(iii) Swimming pools, deck and pool and ancillary areas.
(iv)
Embalming enclosures, autopsy enclosures.
(v)
Operating and delivery enclosures.
(vi)
Warehouses for products that give off odours
(e.g. particleboard products such as formaldehyde).
or
noxious
gases,
(c)
Any enclosure required to be ventilated by a general or local exhaust ventilation
system.
(d)
Any enclosure that contains specific contaminants.
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AS 1668.2—2012
18
2.7 OUTDOOR AIR MIXING AND DISTRIBUTION
A reasonably uniform distribution of outdoor air shall be achieved throughout the occupied
zones for each enclosure, irrespective of whether the outdoor air is—
(a)
introduced separately into the enclosure; or
(b)
mixed with the recycle air in a central plant or local plant (e.g. fan-coil or active
chilled beams).
C2.7 As it is not possible to measure the proportion of effective outdoor air and its
distribution in the air supply duct, the requirements of this Clause will be satisfied if the
system design provides for minimum outdoor air to be carried at all times by the supply
ducts from the air-handling plant to all enclosures and sufficient mixing of outdoor air
with the recycle air in the air-handling plant to supply all enclosures with air of about
the same ratio of outdoor to recycle air.
It may be practicable to express the aim of this Clause in a particular enclosure by the
introduction of ventilation air in a limited number of places, provided that the airflow in
the enclosure is adequately arranged.
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The effects of partitioning
The partitioning of floor areas (for example, during refurbishments) can affect the
performance of the ventilation system. These problems can occur if partitioned offices
are installed in areas with ventilation systems designed for open plan floor space and
no review of the ventilation system is undertaken. The review may indicate a need to
provide additional transfer grilles (in doors or walls) or additional supply/return air
grilles in partitioned offices if these have been left with no local return grilles. If these
alterations are not carried out, the ventilation effectiveness of the existing system may
be reduced.
Even small-scale alterations to layouts can cause problems if partitions or walls are
placed in locations that impede the flow of air. Other obstructions to airflow, such as
large arrays of demountable panels and bookshelves, can reduce ventilation
effectiveness, even in an open plan office.
2.8 OUTDOOR AIRFLOW RATES
2.8.1 General
The minimum effective outdoor airflow rate required by Appendix A shall be provided to
each enclosure(s) served by a ventilation system. This may be achieved by—
(a)
bringing in outdoor air directly into the system;
(b)
using residual outdoor air in recycle or transfer airstreams;
(c)
using air-cleaning devices to provide an equivalent outdoor air effect; or
(d)
by a combination of all of the above.
The combination of all these outdoor air types or strategies is called effective outdoor air.
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19
AS 1668.2—2012
Ca l c ul ate m i ni m u m ef fe c tive
o u td o o r a i r f l ow r ate
B a s e d o n a r e a?
Ye s
C a l c u l a te m i n i m u m
C l a u s e 2. 8 .4.1
Ye s
C a l c u l a te m i n i m u m
C l a u s e 2. 8 .4. 2
Ye s
Ca lculate ef fe c tive
Clau s e 2. 8.5. 2
Ye s
Ca lculate ef fe c tive
Clau s e 2. 8.5. 3
Ye s
Ca lculate ef fe c tive
Cl a u s e 2. 8. 5.4
No
No
Based on occupancy?
S i n g l e e n c l o s u r e?
or
10 0% o u td o o r a i r
No
M u l t i p l e e n c l o s u r e?
or
r e c yc l e a i r ?
No
Fa c to r m o di f i c ati o n of th e
ef fe c tive o u td o o r a i r
(f il te r s , r e s i d u a l, t r a n s fe r)?
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No
Check minimum introduced
o u td o o r a i r
Ye s
C a l c u l a te m i n i m u m
C l a u s e 2. 8 . 2
EN D
FIGURE 2.2 FLOW CHART ON THE APPLICATION ON SECTION 2.8
2.8.2 Minimum required outdoor airflow rate
The minimum amount of introduced outdoor air required for the system (Qf) shall be
calculated as the greater of the area-based minimum and the occupancy-based minimum as
follows:
(a)
Area-based minimum:
Qf = A  0.35 L/s.m2 .
A2
(b)
. . . 2.8.2(1)
Occupancy-based minimum:
Qf = n  qf
. . . 2.8.2(2)
(where the system provides 100% outdoor air or filtration in accordance with
Appendix D is not proposed for a single enclosure system)
or
Qf = (n  qf)  M
. . . 2.8.2(3)
(where the system provides 100% outdoor air or filtration in accordance with
Appendix D is not proposed for a multiple enclosure system)
or
Qf = n  7.5 L/s
. . . 2.8.2(4)
(where only particulate filtration in accordance with Appendix D is proposed for a
single enclosure system)
or
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 Standards Australia
AS 1668.2—2012
A2
20
Qf = (n  7.5 L/s)  M
. . . 2.8.2(5)
(where only particulate filtration in accordance with Appendix D is proposed for a
multiple enclosure system)
or
Qf = n  2.5 L/s
. . . 2.8.2(6)
(where particulate filtration and odour treatment in accordance with Appendix D are
proposed for a single enclosure system)
or
Qf = (n  2.5 L/s)  M
. . . 2.8.2(7)
(where particulate filtration and odour treatment in accordance with Appendix D are
proposed for a multiple enclosure system).
2.8.3 Minimum required effective outdoor airflow rate
The minimum required effective outdoor airflow rate provided by a mechanical ventilation
system to each served enclosure shall comply with Clauses 2.8.4 to 2.8.7.
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The minimum effective outdoor airflow required for each enclosure shall be calculated on
the basis of either the area of the enclosure (Clause 2.8.4.1) or the number of occupants in
that enclosure (Clause 2.8.4.2) as required by Appendix A.
The minimum effective outdoor airflow supplied to an enclosure may be calculated for
simple systems by using Clause 2.8.5.2 and Clause 2.8.5.3 and for more complex systems
that incorporate features such as transfer air, local air cleaning or central air cleaning by
using Clause 2.8.5.4.
C2.8.3 The amount of effective outdoor airflow supplied to an enclosure may be
modified by additional factors such as the use of residual effective outdoor airflow
recycled from other enclosures, transfer air from adjacent enclosures, supply air
cleaning, recirculation air cleaning, central recycle air cleaning and the use of variable
air volume. Typically, the use of residual effective outdoor airflow recycled from other
enclosures, transfer air from adjacent enclosures, supply air cleaning, recirculation air
cleaning, and central recycle air cleaning will tend to increase the amount of effective
outdoor airflow, while the use of variable air volume may tend to reduce the amount of
effective outdoor airflow under certain conditions.
2.8.4 Minimum effective outdoor air
2.8.4.1 Based on area of the enclosure
For an enclosure where the minimum outdoor airflow rate in Appendix A is based on the
area of the enclosure [litres per second per square metre (L/s.m2 ) of floor area], the
minimum effective outdoor airflow rate (q min) shall be as follows:
A2
q min = q fA
where
A2
q f = the minimum effective outdoor airflow rate given in Appendix A, in litres per
second per square metre of the floor area
A = the area of the enclosure, in square metres
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21
AS 1668.2—2012
2.8.4.2 Based on the number of occupants in the enclosure
For an enclosure where the minimum outdoor airflow rate in accordance with Appendix A
is based on the number of occupants (litres per second per person), the minimum effective
outdoor airflow rate (q min) shall be as follows:
A2
q min = q fN
where
A2
q f = the minimum effective outdoor airflow rate given in Appendix A, in litres per
second per person
N = the occupancy, in accordance with Clause 2.2.2
2.8.5 Calculation of effective outdoor airflow rate
2.8.5.1 General
The effective outdoor airflow rate shall be in accordance with Clauses 2.8.5.2, 2.8.5.3 or
2.8.5.4 as applicable.
2.8.5.2 Air-handling system serving a single enclosure or providing 100% outside air
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For an air-handling system serving a single enclosure, or supplying 100% outdoor air with
no additional factors that might modify the quantity of effective outdoor airflow, the
effective outdoor airflow rate shall be equal to the outdoor air component of the supply
airflow rate. For these systems the minimum introduced outdoor airflow rate (Qf) shall be
the sum of the required minimum effective outdoor airflow rates for all enclosures served,
as follows:
Qf  q min
2.8.5.3 Air-handling system supplying air to multiple enclosures
For an air-handling system supplying air to multiple enclosures with recycle air, the
effective outdoor airflow rate may be different to the introduced outdoor air component of
the supply airflow rate. If there are no additional factors that might modify the quantity of
effective outdoor airflow, the minimum introduced outdoor airflow rate (Qf) shall be the
sum of the required minimum effective outdoor airflow rates (q min) for all enclosures
served multiplied by the multiple enclosure factor (M), as follows:
Qf  Mq min
where
M = the multiple enclosure factor
=
1
1  R  rc 
R = the ratio of the sum of required effective outdoor airflow rates for all
enclosures served to the total supply air for all enclosures served
=
q
q
min
s
rc = the highest ratio, for any of the enclosures served, of effective outdoor
airflow required by Clauses 2.8.4 to the corresponding supply air
q

min
= max q 
s
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 Standards Australia
AS 1668.2—2012
22
2.8.5.4 For an air-handling system that includes factors that might modify the quantity of
effective outdoor air
For an air-handling system where there are factors that might modify the quantity of
effective outdoor air, the minimum introduced outdoor airflow rate (Qf) shall be that
required to satisfy the minimum required effective outdoor airflow determined by
Clause 2.8.3 to all enclosures, calculated using ventilation airflow analysis in accordance
with Appendix D.
2.8.6 Variable air volume systems
For a system with a variable supply airflow rate, provision shall be made to ensure that the
minimum effective outdoor airflow rate complies with Clauses 2.8.3, under all operating
conditions. For the purpose of this Clause, groups of enclosures used for a similar purpose
and subject to the same density of occupancy and pro rata rate of supply air, such as general
office space, may be regarded as a single enclosure.
NOTE: The requirements of Clause 2.8.3 at reduced flow rates vary as the distribution of air to
the enclosures changes.
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C2.8.6 One way of satisfying the requirements of this Clause, is to introduce into the
air-handling plant sufficient outdoor air. In this case, the outdoor air content in the air
supplied by the air-handling plant is determined by the use of the highest ratio of
outdoor air to total supply air for any enclosure, applied to the total of air supplied to
all enclosures. This solution satisfies the Standard but may not be economical since all
enclosures with lower ratios are oversupplied with outdoor air.
The calculations in this Section are based on the fact that air returned from enclosures
oversupplied with outdoor air still has some potential to dilute pollutants to satisfactory
levels when introduced into the supply duct from the air-handling plant to enclosures. It
should be evident that further economies can be achieved by the grouping of enclosures
with like ratios of outdoor air to total air on the same air-handling plant. This solution
may not be possible or appropriate in many cases for a variety of reasons.
Under certain circumstances, variable air volume systems are known to reduce the
amount of effective outdoor air suppled to an enclosure via the supply air systems and,
as such, these systems require further assessment of introduced outdoor airflow rates
filtration and possibly lead/lag provisions. Areas such as meeting rooms may require a
dedicated outdoor supply.
2.8.7 Make-up air requirement
For a system serving enclosures from which make-up air for general or local exhaust is
drawn, the outdoor air shall be in accordance with Clause 3.8.
2.9 OUTDOOR AIRFLOW ADJUSTMENT
2.9.1 Systems serving enclosures in which the temperature may exceed 27°C under
normal operation
During periods of normal operation when the temperature in the enclosure is expected to
exceed 27°C, the introduced outdoor airflow rate shall be increased to a minimum of 15 L/s
per person or appropriate odour filtration (recycle, recirculated or supply air) shall be
provided to achieve equivalent effective outdoor airflow. Where necessary, adjustment may
be controlled manually or automatically.
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23
AS 1668.2—2012
C2.9.1 It is well recognized that additional body odour is generated at elevated
temperatures and/or that the perception of body odours is enhanced under these
conditions. Where temperatures in excess of 27°C occur under normal operation, rates
will need to be adjusted upwards to compensate for increase in body odour generation
or perception by occupants. Otherwise appropriate odour filtration should be provided
to achieve the same resulting effective outdoor airflow.
2.9.2 Systems serving enclosures with transient or variable occupancy
During periods of low occupancy, the introduced outdoor airflow rate may be adjusted to
the flow rate appropriate to the low occupancy.
When contaminants are generated independent of occupants or their activities and the
contaminants do not present a short-term health hazard, air-handling systems may be shut
off during unoccupied periods.
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When contaminants, other than those associated with occupants, are dissipated by natural
means during unoccupied periods, the increase in outdoor airflow rate may lag behind the
increase in occupancy provided the following conditions are met:
(a)
The lag time between increases in occupancy and the adjustment does not exceed that
determined in Figure 2.3.
(b)
If the adjustment is subject to manual control, the control is operable from the
enclosure with the largest occupancy load or from another appropriate location.
(c)
If the adjustment is subject to automatic control, means to be provided to manually
override the automatic control.
(d)
The means of adjustment and of control of adjustment to ensure that contaminants do
not exceed acceptable levels during occupied periods.
Where specific contaminants that require the provision of general or local exhaust systems
continue to be generated in the enclosures during unoccupied periods, the increase in
introduced outdoor airflow shall lead the increase in occupancy by a time not less than that
shown in Figure 2.4.
NOTE: Rationale for lag or lead time for transient occupancies is provided in Appendix G.
C2.9.2 Although a system may be turned off during periods of non-occupancy, a period
of post-purging by natural or mechanical means may be needed after departure of
occupants to clear pollutants generated by the occupants. Also a period of pre-purging
may be required before entry of occupants to clear accumulation of pollutants
generated by furnishings, other materials, and the like, within the space.
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 Standards Australia
AS 1668.2—2012
24
10 0
50
50
0
(E
nc
lo
su
re
vo
m
e
pe
r
pe
rs
on
)
3
m
/p
er
0
n
10
so
40
30
25
20
15
10
L /s .PER S O N O U T D O O R A I R
lu
50
10.0
5.0
5
2.
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5
0. 5
1.0
5.0
1.0
10.0
TIME, h
FIGURE 2.3 PERMISSIBLE LAG TIME—HOURS
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 Standards Australia
25
AS 1668.2—2012
10 0
50
0
50
10
0
50
3
m
25
vo
m
20
lu
e
15
pe
r
rs
10
pe
on
)
5
2.
5.0
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5
0. 5
L /s .p e r s o n O U T D O O R A IR
n
re
30
su
so
40
lo
er
nc
/p
(E
10.0
1.0
5.0
1.0
10.0
TIME—h
FIGURE 2.4 PERMISSIBLE LEAD TIME—HOURS
2.9.3 Demand control ventilation (DCV)
During periods where occupancy is less than design (n), demand control ventilation (DCV)
may be used to reduce the amount of introduced outdoor airflow in proportion to the actual
enclosure population.
When the actual occupancy is below the maximum occupancy assumed for system design,
the occupancy-based outdoor air rate may be reduced accordingly, but not below the
minimum area-based outdoor air ventilation rate of 0.35 L/s/m2.
Where a group of enclosures are supplied by a single air-handling system, each enclosure
shall have its actual population demand included in the control strategy for the volume
control of introduced outdoor airflow.
Population indicators shall provide a reasonably accurate representation of the actual
population (e.g. an occupancy schedule based on a known pattern of occupancy or various
sensor applications).
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 Standards Australia
AS 1668.2—2012
26
DCV is most suitable for large single enclosures with transient occupancy but may be
applied to any enclosure. In multiple enclosure systems, population indicators shall be
placed in each enclosure served by the system.
C2.9.3 Demand control ventilation (DCV) is an optional control strategy, whereby the
introduced outdoor airflow is modulated (controlled) in response to the actual
occupancy (demand) of each enclosure served. When the actual occupancy is below the
maximum occupancy assumed for system design, the occupancy-based outdoor air rate
may be reduced accordingly. Population indicators that are used have to provide a
reasonably accurate representation of the current enclosure occupancy.
Population indicators that may be suitable for DCV include CO 2 , mixed gas detection,
occupancy sensors, and occupancy schedules. Temperature sensing alone is not
considered to be an acceptable form of monitoring for demand control.
Where CO2 is used as an indicator, CO2 sensors control the outdoor air intake flow rate
to maintain a predetermined set point or equilibrium level. Typical set points are
600 ppm–800 ppm and should be selected based on the ambient CO2 levels of the site
and the enclosure characteristics.
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CO2 based DCV should not be applied in zones with indoor sources of CO2 other than
occupants.
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 Standards Australia
27
SECTI ON
3
AS 1668.2—2012
MECHANICAL VENTI LATION—
EXHAUST S YSTE M S
3.1 SCOPE OF SECTION
This Section sets out exhaust ventilation requirements for enclosures in which contaminants
are generated or contained, whereby indoor air contaminants are diluted or removed entirely
by exhausting indoor air and providing make-up air.
NOTES:
1 A flow chart on the application of this Section is shown in Figure 3.1.
2 For enclosures used by vehicles with combustion engines, see Section 4.
3 For guidance on a performance-oriented approach to mechanical ventilation design, see
Appendix F.
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C3.1 This Standard allows two approaches to exhaust air dilution—general or local
exhaust. Where enclosures contain processes that generate contaminants of a type or
concentration deemed to be objectionable or that may have adverse health effects
[defined in Clause 3.3.1(a)], it is specified that these be removed directly from the
enclosure by a separate exhaust system and not be recirculated through the supply air
system. It is also required that the exhaust airflow rate be adequate to dilute the
contaminants and be arranged to discharge them outside the building in such a manner
that no danger or nuisance results to people outside the building.
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AS 1668.2—2012
28
S ECT I O N
3
I s th e e n c l o s u r e
n atu r a ll y ve ntil ate d
D o e s th e e n c l o s u r e N o
c o nt a i n ef f l u e nt a s
defined in Clause 3.3.1
Ye s
No
Ye s
No
C o m p l y wi th
general
requirements
Cl au s e 3. 3. 2.1
I s th e e n c l o s u r e of
th e t y p e o r s i m il a r
to th e t y p e s li s te d i n
Table B1, Appendix B.
Lo c a l ex hau s t
ve n t i l a t i o n r e q u i r e d
Ye s
Ye s
R e fe r to oth e r
S t a n d a r d s fo r
oth e r r e q u i r e m e n t s
Lo c a l ex h a u s t to
b e u s e d i n li e u
of a ll o r p a r t of
g e n e r a l ex h a u s t
G e n e r a l ex h a u s t
ve ntil ati o n
required
Comply with
g e n e r a l r e q u i r e m e nt s
of Cl au s e 3. 3. 2.1
No
Ty p e A
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C o m p l y wi th
r e q u i r e m e n t of
Cl au s e s 3. 2.1, 3. 2. 2
a n d 3. 2. 3
Ca l c ul ate ex h a u s t
a i r q u a nti t y f r o m
Ta b l e B1, A p p e n di x B
Ty p e of ef f l u e nt
Ty p e B
H o o d c a ptu r e s
ve l o c i t y n ot l e s s
t h a n 0. 5 m /s (s e e
Cl au s e 3. 3. 2. 2)
Kitchen exhaust hood
to b e p r ovi d e d
in accordance
with Cl au s e 3.4
Ca l c ul ate ex h a u s t
a i r q u a nti t y,
Cl au s e s 3. 5 o r 3.6
En c l o s u r e to
c o m p l y wi th
Cl au s e s 3.7, 3.8
a n d 3.9
A i r di s c h a r g e to
comply with
Clau s e 3.10
EN D
FIGURE 3.1 FLOW CHART ON THE APPLICATION OF SECTION 3
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 Standards Australia
29
AS 1668.2—2012
3.2 EXHAUST VENTILATION
3.2.1 General
Unless naturally ventilated, enclosures listed in Appendix B require general exhaust
ventilation. Exhaust airflow rates shall be as specified in Appendix B.
Supply air ventilation may be used as an alternative to exhaust air systems in accordance
with Clause 1.2.2(b)(ii).
NOTE: Local exhaust air systems that can be demonstrated as being effective in the removal of
effluent may be used in lieu of part or whole of the general exhaust ventilation
(see Clause 1.2.2(b)(ii)).
C3.2.1 Appendix B of this Standard specifies rates for general exhaust ventilation.
These rates are deemed adequate except for such applications as bathrooms, laundries
and hospital sterilizing rooms where excessive heat or steam is generated, or sanitary
compartments where excess odours are generated. In kitchens where the size of cooking
apparatus exceeds the limits stated, local exhaust should be used in addition to the
specified general exhaust.
3.2.2 Exhaust locations
As far as practicable, exhaust-air intakes that are used for general exhaust-air collection
shall be located on the opposite sides of the enclosure from the sources of make-up air, to
ensure that the effluents are effectively removed from all parts of the enclosure.
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3.2.3 Enclosures served by both supply and general exhaust systems
Where the enclosure is served by both a supply air system and a general exhaust system
required by this Section, the exhaust airflow rate shall exceed the supply airflow rate by at
least 10%, unless means are provided to maintain any adjacent enclosure, of a different use,
at a higher pressure at all times.
C3.2.3 The aim of the requirement for the general exhaust rate to exceed the supply
rate (where used) by 10% is to ensure that effluent cannot flow to adjacent enclosures.
Where mechanical ventilation is used to produce pressure differentials between
enclosures or where a specified general exhaust is replaced by a local exhaust system,
this requirement for general exhaust to exceed supply may be waived.
Consideration of AS 5601.1 is of particular importance for enclosures containing openflued gas heating appliances.
3.3 LOCAL EXHAUST
3.3.1 Types of effluent requiring local exhaust
Effluent having any one or more of the following properties shall be removed by local
exhaust in accordance with Clause 3.3.2.
(a)
Type A Significant localized sources of toxic, irritant, asphyxiant, offensive,
flammable or explosive gases, dusts, fumes or vapours, excluding effluent arising
from cooking processes and contaminants controlled in accordance with Section 2
and/or Section 4 (excluding direct ducting from tail pipes in accordance with
Clause 4.5.3.2) or Appendix B.
(b)
Type B Heated air with or without water or grease vapour produced by cooking or
dishwasher equipment employed for the preparation of food for commercial or
institutional purposes and having a total maximum input exceeding 8 kW for an
electrical appliance, or total gas input 29 MJ/h for a gas appliance, or any deep fryer
appliance, or more than one item of apparatus within a room and having a total
maximum power input exceeding 0.5 kW/m2 (1.8 MJ/m2 for gas appliances) of floor
area of the enclosure.
A1
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AS 1668.2—2012
A2
30
The following shall be exempted from this requirement:
(i)
Commercial coffee machines of all sizes.
(ii)
Microwave cookers and similar low-power cooking equipment used for commercial
purposes, which are used infrequently or used solely for the purposes of reheating
food.
(iii) Apparatus used specifically for space heating.
(iv)
Apparatus in plant enclosure.
(v)
Apparatus used solely for domestic purposes.
(vi)
Apparatus that does not cause objectionable conditions in the enclosure.
C3.3.1 Typically, Type A effluents are emitted by welding processes, chemical and
microbiological reactions, degreasing tanks, acid tanks and certain woodworking
operations. Type B effluents are more of a nuisance than dangerous, and the most
common application would relate to kitchen exhaust hoods.
3.3.2 Effluent removal
3.3.2.1 General requirements
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The removal of effluent by means of local exhaust shall be as follows:
(a)
The effluent shall be collected as it is being produced, as close as practicable to the
source of generation, using special surroundings, hoods, surface-mounted exhaust-air
intakes and similar means. The airflow rates shall be such as will ensure positive
capture and removal of the effluent.
(b)
Local exhaust shall be permitted to complement and/or substitute for general exhaust.
(c)
Make-up air openings, or mechanical ventilation system air outlets to an enclosure in
which an exhaust hood is situated, shall be distributed and designed so as not to be
detrimental to the performance of the hood, or cause excessive cross-draughts over
any ventilated apparatus. Outdoor air for make-up shall be introduced so as not to
adversely affect air-conditioning systems.
NOTE: Subject to documentary evidence of performance, proprietary exhaust hoods
incorporating make-up air systems are considered to meet the requirements of this Clause.
(d)
Sufficient airflow shall be suitably distributed over exhaust hoods to effectively
capture and convey all convected heat fumes and other aerosols to hood exhaust
openings.
NOTE: Local exhaust airflow rates vary depending on the application. Users and designers should
refer to relevant guidance material, including Standards for applications outside the scope of this
document. Some of the relevant Australian Standards are included in Appendix O. In the absence
of relevant Australian Standards, the current recommendations that appear in the ACGIH
Industrial Ventilation: A Manual of Recommended Practice should be adopted.
C3.3.2.1 Apart from establishing requirements for local exhaust, the Standard does not
attempt to prescribe the form, hood velocities or airflow rates of hoods or other means
used for local exhaust of effluents with the exception of kitchen exhaust. Australian
Standards for the design of laboratories should be referred to in regard to local exhaust
and make-up air provisions in such applications.
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 Standards Australia
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AS 1668.2—2012
3.3.2.2 Type A effluent removal
In addition to the requirements of Clause 3.3.2.1, the velocity of the air, as it enters the
capture device surrounding the source of Type A effluent generation, shall be not less than
0.5 m/s averaged across each opening in the capture device. For the purposes of this Clause,
the capture device shall be deemed to comprise the exhaust hood as well as any impervious
walls, floors or benchtops that, together with the exhaust hood, serve to contain the source
of effluent generation.
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C3.3.2.2 This Standard is not intended to apply to materials of duct or hood
construction, industrial process system design, ignition prevention, explosion venting,
pneumatic conveying systems, fire safety venting and other aspects of ventilation system
design and installation that are dependent on the process, the product and materials
used in industrial ventilation systems. Where specific industrial processes require
special ventilation systems to suit such processes, including conveying of Type A
effluents [refer to examples (a) and (b) below], the design and construction of these
ventilation systems should be in accordance with the requirements of relevant
Standards, industry guidelines and requirements of authorities. In the absence of
requirements of authorities, codes of practice and/or relevant Standards, the
recommendations of the ACGIH Industrial Ventilation: A Manual of Recommended
Practice should be adopted (refer to Appendix O).
(a) Where flammable atmospheres could be present as a consequence of dusts, gases or
vapours within an occupied enclosure or within exhaust ductwork, the exhaust
ventilation systems, including materials and methods of duct construction should be
designed and constructed to mitigate ignition, flammability and/or explosion risks,
in accordance with requirements of authorities, relevant codes of practice and
Standards (e.g. grain milling dust removal, spray painting booth ventilation
systems, etc.).
(b) Where toxic, irritant, asphyxiant or offensive dusts, gases or vapours could be
present in an occupied enclosure, within exhaust ductwork or in airstreams
discharged to atmosphere, personnel inside and outside the building should be
protected from being harmed by such materials by exhaust ventilation systems that
are designed and constructed in accordance with requirements of authorities,
relevant Codes of practice and Standards (e.g. welding booth exhaust, fume
cupboards, etc.).
3.3.2.3 Type B effluent removal
Hoods shall be provided for the collection of Type B effluent. Where the apparatus
specified in Clause 3.3.1(b) is a cooking appliance, a kitchen exhaust hood complying with
Clause 3.4 shall be installed above the appliance.
3.3.2.4 Grease vapour
A2
Where Type B effluent is likely to include grease vapour, the kitchen exhaust hood shall be
provided with a grease removal device in accordance with Paragraphs E5 and/or E6,
Appendix E.
3.4 KITCHEN EXHAUST HOODS
3.4.1 General
A2
Requirements for kitchen exhaust hoods are set out in this Clause for the seven common
types and configurations of hoods that apply to the seven most common types of cooking
processes. Clause 3.5 sets out a prescriptive procedure for hood design. Required kitchen
exhaust hoods shall comply with Clause 3.5 or 3.6. Construction and installation
requirements of kitchen exhaust hoods shall be in accordance with Appendix E.
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AS 1668.2—2012
32
Alternative exhaust hood designs, including proprietary designs, engineered ventilated
ceiling systems and specialized (application specific) designs, may be used provided it can
be established that the performance of such systems is at least equivalent to the
performance of the hoods described in this Section.
A2
NOTE: Hood types 5 and 7 may be used as per Clause 3.6.
3.4.2 Hood and cooking process types
3.4.2.1 General
The seven common types and configurations of hoods and the seven types of cooking
processes are defined in Clauses 3.4.2.2 and 3.4.2.3.
3.4.2.2 Hood type nomenclature
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Hood type nomenclature is as follows (refer also to Appendix E):
(a)
Hood Type 1 Low sidewall where the canopy does not extend at least 150 mm
beyond the edge of the cooking surface (see Figure E3, Appendix E).
(b)
Hood Type 2 Corner-mounted, subject to a maximum length to width ratio of 2:1
(see Figure E4, Appendix E).
(c)
Hood Type 3 Sidewall (see Figure E5, Appendix E).
(d)
Hood Type 4 Island (see Figure E6, Appendix E).
(e)
Hood Type 5 Ventilated ceiling (see Figure E12, Appendix E).
(f)
Hood Type 6 Eyebrow hood (see Figure E10, Appendix E).
(g)
Hood Type 7 Proprietary equipment.
3.4.2.3 Cooking process type nomenclature
Cooking process type nomenclature is as follows:
A2
A2
(a)
Process Type 1 Non-grease-producing equipment and void spaces under the hood,
which serve to ventilate other cooking equipment.
(b)
Process Type 2 Low-grease, medium-heat-producing equipment such as griddles,
ranges, salamanders, conventional fryers, tilting skillets, steam kettles, gas ovens and
induction cookers.
(c)
Process Type 3 High-grease, low-heat-producing equipment such as electric deep-fat
fryers, grooved griddles, hot tops and hot top ranges.
(d)
Process Type 4 High-grease, medium-heat-producing equipment such as countertop
barbecues and gas-fired deep fat fryers.
(e)
Process Type 5 High-grease, high-heat-producing equipment, and open flame
charcoal equipment utilizing solid fuel.
(f)
Process Type 6 Oriental cooking tables and/or woks.
(g)
Process Type 7 Bread ovens and steam-producing combination ovens.
3.4.3 Hoods serving non-grease-producing equipment
Where an exhaust hood is located over a dishwashing machine, non-grease-producing oven
or other non-grease-producing equipment item, and serves only that type of equipment,
grease filtration is not required and the exhaust airflow rate shall provide a hood face
velocity of not less than 0.3 m/s.
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33
AS 1668.2—2012
As an alternative, to reduce exhaust airflow rates and fan energy consumption, hoods
serving dishwashing machines and ovens under Process Type 1 (see Clause 3.4.2.3(a))
above are permitted to operate with an exhaust airflow rate that provides a hood face
velocity of not less than 0.1 m/s, provided that the hood overhangs the edge of the
dishwashing machine opening or the oven door by at least 300 mm on all sides (except on
sides adjoining a wall) and is at least 300 mm deep, at all points in the hood, from the upper
inside hood surface to the hood gutter. The minimum contained volume of the canopy
formed by the hood shall be not less than 0.3 m3. Where ceiling heights prevent a hood
depth of 300 mm, the hood shall be as deep as possible, and shall have a contained volume
of not less than 0.3 m3.
NOTE: For the purposes of this Clause, the hood face velocity is the velocity of the airflow
through the horizontal plane bounded by the vertical sides of the hood.
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C3.4.3 Dishwashing machines and ovens are opened intermittently and, when opened,
release large volumes of steam and/or hot air for short periods of time. To minimize
nuisance to occupants, to avoid staining of ceilings and to prevent condensation on
nearby walls and ceilings, exhaust hoods are required to be provided for these items.
Where these items of equipment do not produce grease vapours, grease removal devices
are not required; however, the intermittent opening of oven and dishwasher doors
requires hoods with adequate exhaust airflows or with sufficient volume to capture and
hold the large, but brief, flow of steam or hot air, until it is vented via the kitchen
exhaust system.
Although hoods serving dishwashing machines and ovens may not be handling greaseladen contaminants, they are a potential source of nuisance odour and moisture
generation, and thus required to be connected to kitchen exhaust systems complying
with other relevant clauses of this Standard.
A2
A2
3.4.4 Specific cooking devices
For front- and rear-opening, standalone cooking devices (for example, pizza ovens, tunnel
ovens, combi ovens), hood length/width shall be configured so that an overhang of at least
300 mm extending beyond the opening of the cooking equipment is ensured. For equipment
with front-mounted doors, an overhang in accordance with Clause 3.5 shall be achieved.
Installation lengths/heights deviating from this are possible for special function hoods (grill
hood, bar hood/counter hood).
3.4.5 Proprietary exhaust allowance
Where kitchen appliances are provided with proprietary exhaust systems, that is, exhaust
spigots ready for connection to an exhaust system, the exhaust airflow rate shall be in
accordance with the manufacturer’s requirements. In this case, omission of separate exhaust
hoods shall be permitted (see Clause 3.4.1).
3.4.6 Charcoal and solid fuel appliances
All hoods and associated exhaust systems for use over charcoal and solid fuel appliances
shall be provided with separate systems, and shall not be combined with a system serving
grease- or oil-generating or oil-heating appliances.
NOTE: Where the exhaust air is likely to significantly pollute the ambient air, the exhaust
discharge may be required to be treated to reduce the concentration of contaminants. Reference to
authorities is recommended for requirements relating to the quality and concentration of
discharge contaminants.
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AS 1668.2—2012
34
3.5 KITCHEN EXHAUST HOOD AIRFLOW—PRESCRIPTIVE PROCEDURE
The exhaust airflow rate (Q) for a hood shall be calculated using one of the equations set
out in Table 3.1. The particular equation used in calculating the exhaust airflow rate shall
be dependent on the worst case. For example, where a Type 4 cooking process is located
under the same hood as a Type 2 cooking process, the equation applicable to the Type 4
cooking process shall be used for the entire hood. The calculated exhaust airflow rate shall
be not less than 250 L/s/m2 of cooking surface.
NOTE: For oven applications, the cooking surface area is deemed to be equivalent to the oven
door area.
The equations of Table 3.1 are based on a minimum overhang, beyond the edge of the
cooking surface or point (location) of discharge of effluent if not from cooking surface, of
150 mm for cooking processes Types 1 to 4, 300 mm for cooking processes Type 5,
600 mm for cooking process Type 6 and 450 mm for cooking process Type 7. The face of
Type 1 hoods shall not exceed a maximum horizontal setback of 300 mm from the leading
edge of the kitchen appliance. The length of the hood shall be not less than the length of the
kitchen appliance.
NOTE: Fan-forced cooking appliances may require more detailed consideration of overhang due
to the increased penetration of the effluent into the enclosure.
TABLE 3.1
CALCULATION OF MINIMUM HOOD EXHAUST AIRFLOW RATE
Cooking process
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Hood type
Hood Type 1
Low sidewall
Type 2
Type 3
Type 4
Type 5
Type 6
Type 7
Q = 400  L
Q = 600  L
Q = 800  L
Q = 800  L
N/A
N/A
Hood Type 2
Corner mounted
Hood Type 3
Sidewall
Q = 190  P  H Q = 190  P  H Q = 375  P  H Q = 375  P  H Q = 320  P  H Q = 320  P  H
Hood Type 4
Island
Hood Type 6
Eyebrow
Q = 250  P
N/A
Hood Types
5+7
N/A
N/A
NA
Q = 250  P
As per manufacturer’s requirements
where
Q
= exhaust airflow rate, in litres per second
L
= inside length of hood, in metres
W = inside width of hood, in metres
P
= inside perimeter of hood over all exposed sides, in metres
H
= height of hood above cooking appliance, in metres
Calculation of inside perimeter (P)
Hood Type 2
Corner mounted P = W + L
Hood Type 3
Sidewall
P = 2W + L
Hood Type 4
Island
P = 2W + 2L
Hood Type 6
Eyebrow
P = 2W + 2L
NOTE: For cooking process Type 1, refer to Clause 3.4.3.
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35
3.6 VENTILATED CEILINGS AND
EQUIPMENT (HOOD TYPES 5 AND 7)
PROPRIETARY
AS 1668.2—2012
KITCHEN
EXHAUST
Ventilated ceilings or proprietary kitchen exhaust hoods not covered under Clauses 3.4
and 3.5 shall be designed to a proven and tested Standard. The basis for these designs is to
lower energy costs by reducing exhaust air requirements and, consequently, they generally
require more detailed calculation methods.
NOTES:
1 The acceptable measure of performance of the equipment (ventilated ceiling or
exhaust hood) is to capture and contain all effluent without spillage.
2 Typical Standards and/or guidelines include the following:
(a) The German guideline VDI 2052, Ventilation equipment for kitchens.
(b) The German Standard DIN 18869, Equipment for Commercial Kitchens—Components
for Ventilation (all parts).
3.7 AIR FROM ENCLOSURES HAVING EXHAUST AIR REQUIREMENTS
3.7.1 General requirements
Air from an enclosure ventilated by a required general or local exhaust system shall not be
recycled to other enclosures of different use.
3.7.2 Air pressures
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The air pressure of enclosures served by a required general exhaust system shall be less
than that of adjacent enclosures not served by required exhaust systems, during normal
operation of the system.
NOTE: This may be evidenced by net airflow from the higher pressure to the lower pressure
combined with no significant transfer of air into the high-pressure area.
C3.7.2 Where it is expected that a negative pressure will exist in an enclosure relative
to outside, it is not recommended that open-flued gas appliances be installed. Refer to
AS 5601.1.
3.8 REPLENISHMENT OF EXHAUST AIR
3.8.1 Source
The air exhausted from enclosures shall be replenished by outdoor air, transfer air or by
make-up air of an acceptable quality from an adjacent enclosure. Make-up air shall not be
drawn from an enclosure ventilated by a required exhaust system or from an adjacent car
park. Make-up air from an enclosure ventilated by a required exhaust system is permitted
for unoccupied enclosures (see Note 1). Where make-up air or transfer air is not available, a
supply air ventilation system shall be permitted. Where the make-up air is drawn from
outside the building, the intake shall comply with Clause 2.3.
NOTES:
1 For example, make-up air from a car park is permitted for a garbage room exhaust system.
2 Make-up air from an enclosure served by a non-required exhaust system in conjunction with a
mechanical supply or natural ventilation system is not prohibited.
3 The use of openable windows for natural ventilation and/or make-up air for exhaust systems,
subject to certain conditions, may meet the requirements of regulatory authorities. New
buildings have well-sealed facades and occupants often keep windows closed for reasons of
security, particularly in apartment buildings. These factors lead to the following risks:
(a)
Make-up air drawn through gaps and service penetrations does not meet requirements
of Clause 2.3.
(b)
Restricted make-up air paths reduce exhaust airflow rates.
(c)
Inadequate supply or exhaust ventilation reduces the amenity of the indoor
environment.
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AS 1668.2—2012
36
Where designers of ventilation and air-conditioning systems are aware that these risks will be
present, allowance should be made for make-up air paths complying with Clause 2.3.
Acceptable methods include—
(i)
permanent natural ventilation openings meeting the requirements of this Standard; or
(ii)
a supply ventilation system in accordance with this Standard (whether untreated,
tempered or air-conditioned).
C3.8.1 The increasing implementation of energy-saving building facades via owner’s
choice or government regulation has created buildings that are more impervious or
airtight than in previous years. Improved airtightness means that the de facto natural
ventilation (leakiness) of older style construction no longer provides an easy make-up
airflow path for exhaust systems. A further factor affecting building airtightness is a
generally heightened concern in the community for security of the home. Ventilation via
open windows only occurs when the occupants are at home and, even then, many
occupants close all windows at night for reasons of security or to save air-conditioning
energy consumption during hot or cold weather.
These factors, applying mainly to sole occupancy units in apartment buildings, mean
that day-long natural ventilation with outdoor air is significantly reduced and make-up
air for exhaust systems is no longer drawn from open windows and doorways, but from
gaps in door and window frames, structural cracks and imperfect sealing of service
penetrations. Problems that arise are from such factors are the following:
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(a) Sources of make-up airflow not meeting the requirements of Clause 2.3 to avoid
contamination of outdoor air.
(b) At those few points where air can leak into the building, localized deposits of dust
and staining occur where make-up air enters at high velocity through narrow gaps
and cracks.
(c) Significant pressure losses in the make-up airflow path lead to reduced exhaust
ventilation for many hours each day when the apartment is locked.
(d) Insufficient natural ventilation with outdoor air prevents dilution of odours and
increases the risk of mould growth on cool surfaces where moisture can condense.
Designers of exhaust ventilation systems in apartment buildings are advised to provide
paths for make-up airflow via paths complying with Clause 2.3. This is of particular
importance for enclosures containing open-flued gas heating appliances. Designers of
apartment buildings where air-conditioning systems are to be installed (or may be
installed in the future) should consider whether the regulatory allowance for natural
ventilation via openable windows will be sufficient for adequate ventilation. In both
cases, permanent natural ventilation, ducted outdoor air ventilation or even a tempered
mechanical supply ventilation system may be required to fulfil the objective of this
Standard and/or local regulations.
3.8.2 Amount
Where the enclosure adjacent to the exhaust enclosures (and from which make-up air is
being drawn) is itself served by supply ventilation systems, the outdoor airflow rate to these
supply ventilation systems shall be increased, as necessary, to accommodate the amount of
make-up air required for the exhaust ventilation system.
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AS 1668.2—2012
3.8.3 Make-up air for kitchen exhaust hoods
For the purposes of make-up air to a kitchen exhaust hood system, air may be drawn from
the kitchen enclosure or adjacent enclosure (subject to the requirements of Clause 3.8.1),
except that—
(a)
if outdoor air supply to the relevant kitchen enclosure (e.g. via adjacent grilles or
diffusers) or adjacent enclosure is insufficient to offset the kitchen hood exhaust rate,
then make-up air shall be provided directly to the kitchen exhaust hood; and
(b)
if the relevant kitchen exhaust enclosure or adjacent enclosure is air-conditioned,
outdoor air to these spaces shall not be increased above the requirement of Clause 2.8
by more than 1000 L/s.
Where air drawn from the enclosure or adjacent air-conditioned enclosure is not provided
with sufficient outside air to offset the exhaust rate, make-up air for the kitchen hood shall
be provided directly to the enclosure in which the kitchen hood is located.
Outdoor air shall be provided in accordance with this Standard.
3.8.4 Pressure drop
Openings required in enclosure walls, ceilings or floors to allow passage of make-up air
from adjacent enclosures or outside the building shall be of adequate size to ensure that the
pressure drop between enclosures does not exceed 12 Pa.
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C3.8.4 Where it is expected that a negative pressure will exist in an enclosure relative
to outside, it is not recommended that open-flued gas appliances be installed. Refer to
AS 5601.1.
3.8.5 Electrical interlocking of exhaust and supply air
When a local exhaust system requires a mechanical supply air system to replenish exhaust
air, the system shall be interlocked so that the supply system will always run when the
exhaust system is operated.
3.9 COMBINATION OF EXHAUST SYSTEMS
Exhaust air systems that serve different types of enclosures shall be kept separate unless
they are of a similar nature. Enclosures that are similar in nature may be served by common
exhaust systems, and are grouped in Table 3.2.
C3.9 Duct connections between enclosures in different groupings may present a crosscontamination problem when the exhaust system is not in operation. It may also be
unacceptable to combine process exhausts or exhausts from laboratory fume cupboards.
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AS 1668.2—2012
38
TABLE 3.2
ENCLOSURES THAT MAY BE SERVED BY A COMMON EXHAUST SYSTEM
Group
Typical use
1
Airlock, bathroom, change room, laundry, locker room, privacy lock, service sink closet, shower
room, urinal compartment, washroom, water closet compartment
2
Areas where food and beverages are prepared or consumed (e.g. dining room, dishwashing area,
food preparation area, hotel bar, reception area)
3
Plant enclosures (e.g. boiler, machinery, refrigeration enclosures)
4
Compatible process enclosures (e.g. document copying, plan printing, photographic processing
enclosures)
5
Automotive vehicle delivery, parking, pick-up, repair and servicing areas
6
Boundary trap, garbage room, grease trap, sewage ejector enclosures
7
General office exhaust (e.g. tea rooms, kitchenette, office based printing)
NOTES:
1
Where an airlock or privacy lock is provided between an exhausted enclosure and another adjacent
occupied enclosure, make-up air for the exhaust system may be drawn from the adjacent enclosure
through the airlock or privacy lock. Make-up air and relief openings should comply with Clause 3.8. An
airlock or privacy lock is not required to be exhausted separately.
2
Table 3.2 is not intended to be an exhaustive list of possible enclosures.
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3.10 AIR DISCHARGES
3.10.1 General
All exhaust air shall be discharged to atmosphere in such a manner as not to cause danger or
nuisance to occupants in the building, occupants of neighbouring buildings or members of
the public. For the purpose of this Standard, any of the discharges at the flow rates specified
in Table 3.3 shall be deemed to contain objectionable effluent.
Discharges that are not deemed to contain objectionable effluent shall comply with
Clause 3.10.2 and discharges that are deemed to contain objectionable effluent shall comply
with Clause 3.10.3.
TABLE 3.3
OBJECTIONABLE EFFLUENT DISCHARGES
Exhaust-air discharge
Flow rate
Type A effluent as defined in Clause 3.3.1(a)
Any flow rate
Type B effluent as defined in Clause 3.3.1(b)
>1000 L/s (see Clause 3.10.3) (see Note)
NOTE: For the purposes of determination of flow rate, multiple discharges located within a
single 6 m radius shall be treated as a single discharge.
3.10.2 Discharges not deemed objectionable
Air discharges that are not deemed to contain objectionable effluent (see Clause 3.10.1)
shall be in accordance with the following:
(a)
The discharge shall be located and arranged so that the effects of wind, adjacent
structures or other factors do not cause the exhaust airflow rates to be reduced below
the minimum requirement of this Standard.
(b)
The discharge shall be not less than the distance given in Table 3.4 from any outdoor
air intake opening, natural ventilation device or opening.
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39
AS 1668.2—2012
(c)
The discharge shall be emitted to the outside at velocities and in a direction that will
ensure, to the extent practicable, no danger to health or prevent a nuisance from
occurring.
(d)
The discharge shall be not less than the distance given in Table 3.4 from the property
boundary (see Note 1), except that where the dimensions of the property make this
impossible, then the greatest possible distance shall apply. Discharge shall be
permitted on any boundary to a public street that is wider than relevant requirements
of Table 3.4, provided that the distance required by Table 3.4 from an adjacent
property boundary is also met.
NOTES:
1 For the purposes of Clauses 3.10.2 and 3.10.3, the term property boundary means the
boundary between the block of land on which the building in question is constructed and any
adjacent building blocks. The term property boundary does not include Strata Title
boundaries, Community Title boundaries or similar boundaries.
When locating exhaust discharges, designers should consider the possibility that future
installation of an outdoor air intake, openable window or other opening may be within 6 m of
the proposed exhaust discharge point.
2 The choice of a suitable method of discharging air depends on a number of local and
environmental factors as well as the nature and quality of the effluent and the direction and
velocity of the discharge. Generally, it is preferable to discharge exhaust air upwards in a
vertical or near-vertical direction above the roof. Discharges that extend less than 2 m above a
thoroughfare or roof subject to regular traffic are not recommended. Where discharge extends
less than 3 m above a pedestrian thoroughfare, the discharge should be engineered to not
create a nuisance.
3 Where large, relatively clean or high velocity discharges are soundly engineered, separations
less than those specified in Table 3.4 may be acceptable provided that any such engineered
discharges do not significantly pollute the outdoor air.
TABLE 3.4
MINIMUM SEPARATION DISTANCES FROM
DISCHARGES TO INTAKES, BOUNDARY
OR NATURAL VENTILATION DEVICE
Airflow rate within the
minimum distance
L/s
Minimum distance
<200
<400
<600
<800
<1000
1000
1 (see Note)
2
3
4
5
6
m
NOTE: For airflow rates of less than 200 L/s, separation of
discharge from natural ventilation openings within the same sole
occupancy unit do not apply.
3.10.3 Discharges deemed objectionable
Air discharges that are deemed to contain objectionable effluent (see Clause 3.10.1) shall be
in accordance with Clause 3.10.2 and—
(a)
be arranged vertically with discharge velocities not less than 5 m/s;
(b)
for a Type A effluent, be situated—
(i)
at least 3 m above the roof at point of discharge, except that in the case of a
pitched roof, at least 1 m above the ridge;
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AS 1668.2—2012
(ii)
40
above any part of the building (or adjacent building) that is within 15 m
(horizontally) of the discharge point; and
(iii) at least 3 m above a thoroughfare or roof subject to regular traffic, but within
15 m of the discharge point;
(c)
located not less than 6 m from a property boundary (see Notes 1 and 2), any boundary
to a public street, any outdoor air intake opening or any natural ventilation device or
opening; and
(d)
treated to reduce the concentration of contaminants when necessary (see Note 1).
NOTES:
1 Item (d) may be necessary where the ambient air is liable to be significantly polluted by the
discharge. Reference to relevant authorities is recommended for control requirements relating
to concentration of contaminants.
2 For the purposes of Clauses 3.10.2 and 3.10.3, the term property boundary means the
boundary between the block of land on which the building in question is constructed and any
adjacent building blocks. The term property boundary does not include Strata Title
boundaries, Community Title boundaries or similar boundaries.
When locating exhaust discharges, designers should consider the possibility that future
installation of an outdoor air intake, openable window or other opening may be within 6 m of
the proposed exhaust discharge point.
C3.10.3
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Concessions
1
Where it can be demonstrated, by reference to results of independent testing, that
special odour filtration processes will remove the odour contamination from
kitchen exhaust airstreams and prevent exhaust operation if these filters are not in
place, horizontal discharge of kitchen exhausts with airflow rates greater than
1000 L/s may be acceptable. In these cases, for the purposes of applying Table 3.4,
the flow rate may be deemed to be reduced by the actual flow rate multiplied by the
lowest fractional efficiency of the filtration process that is—
Deemed flow rate = Actual flow rate  (Fractional efficiency  Actual flow rate)
2
Where it can be demonstrated, by reference to results of independent testing, that
photochemical or chemical treatment (e.g. UV light, ozone injection or electrostatic
filtration), can remove odour or smoke contamination from kitchen exhaust
airstreams and NOT result in the undue discharge of other contaminants (e.g.
ozone), horizontal discharge of kitchen exhausts with airflow rates greater than
1000 L/s may be acceptable.
3
The use of odour or smoke filtration, photochemical or chemical treatment systems
to achieve concessions on the location, or direction, of exhaust discharges by
removing contaminants, should involve mandatory routine testing and maintenance
to ensure ongoing, satisfactory contaminant removal.
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41
AS 1668.2—2012
3.10.4 Non-required discharges
A2
Spill air and relief air shall be discharged to atmosphere in such a manner as not to cause
nuisance to occupants in the building, occupants of neighbouring buildings or members of
the public.
Where air that has ventilated enclosures within the building is discharged from the building,
it may be redirected to re-enter the ventilation system, provided the net inflow of
uncontaminated outdoor air is not less than that required by Section 2.
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C3.10.4 This provision allows a non-required air discharge point to be located closer
to an outdoor air intake point than would be allowed for a required exhaust air
discharge point and would apply to non-required design provisions such as those
applied to an economy air cycle.
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AS 1668.2—2012
SECTI ON 4
USED BY
42
VENTILATION OF ENCLOSURES
VE HICLE S WIT H COMBUS TION
ENGINES
4.1 SCOPE OF SECTION
This Section applies to all enclosures in which vehicles powered by combustion engines are
parked, serviced or operated (e.g. car parks, automotive service and repair shops, enclosed
driveways, loading docks and similar enclosures). It also provides monitoring requirements
applicable where reduced ventilation rates are adopted as an energy saving measure.
Requirements for specific occupancies located within these enclosures are also given.
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NOTES:
1 A flow chart on the application of Section 4 is shown in Figure 4.1.
2 This Standard does not include requirements for natural ventilation systems, apart from
natural make-up or relief to mechanical systems. Requirements for natural ventilation of car
parks are provided in AS 1668.4.
3 For guidance on a performance-based approach to car park ventilation, see Appendix N.
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43
AS 1668.2—2012
S ECT I O N
4
I s e n c l o s u r e* a
car park?
Ye s
Ca l c ul ate nu mb e r
of c a r s p a c e s
C l a u s e 4. 3 . 2
Does car park require
m e c h a n i c a l ve n t i l a ti o n
No
I s e n c l o s u r e*
an enclosed
d r i veway ?
No
Ye s
Ye s
Ca l c ul ate
ve ntil ati o n r ate
Clau se 4. 5.1
G e n e r a l c o n di ti o n s
Cl a u s e 4.4.1, di s tr ib u ti o n
Cl a u s e 4.4. 2
Ca l c ul ate
ve ntil ati o n r ate
Clau se 4. 5. 2
Simple
procedure
Clause
4.4. 3
No
I s e n c l o s u r e* a
loading
dock?
Ye s
No
Is enclosure an
Ye s
a u to m otive s e r vi c e
/r e p a i r s h o p?
D e t a il e d
procedure
Clause
4.4.4
Ca l c ul ate
ve ntil ati o n r ate
Clau se 4. 5. 3
No
Ye s
Ca l c ul ate
ve ntil ati o n r ate
Clau se 4. 5.4
Combine mechanical
a n d n atu r a l
ve ntil ati o n
I s e n c l o s u r e* u s e d Ye s
by s p e c i a l
p u r p o s e ve hi c l e s?
Ca l c ul ate
ve ntil ati o n r ate
C l a u s e 4. 5 . 5
Comply with
C l a u s e 4.10
I s e n c l o s u r e* a
ve hi c ul a r li f t
o r s h af t?
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No
No
O th e r a r e a s
l o c a te d i n
c a r p a r k a r e a s?
Ye s
Ca l c ul ate
ve ntil ati o n r ate
C l a u s e 4. 2. 2
Ye s
Ca l c ul ate
ve ntil ati o n r ate
C l a u s e 4.6
No
Is enclosure
a q u e ui n g
a r e a?
No
Fi xe d s t af f
e n c l o s u r e?
No
Ye s
Ca l c u l a te s u p p l y
a i r q u a nti t y f r o m
m a x i m u m of
S e c ti o n s 2 a n d 5
i n L /s .m 2
C o m p l y wi th
Clauses
4.7, 4. 8, 4.9
O pti o n fo r e n e r g y
s avi n g 4.11, 4.12
EN D
* En c l o s u r e o r p a r t t h e r e of
a s a p p r o p r i ate
FIGURE 4.1 FLOW CHART ON THE APPLICATION OF SECTION 4
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 Standards Australia
AS 1668.2—2012
44
C4.1 This Standard applies to the provision of mechanical ventilation to enclosures
intended to minimize the potential for adverse health effects from contaminants
generated by combustion engines. The amount of ventilation needed depends on the type
and quantity of vehicles using the enclosures, the time for which vehicles’ engines
operate, and the time that occupants spend in the enclosure. Higher ventilation airflow
should be provided for car parks for which occupants’ exposure is of extended duration
(e.g. parking attendant).
4.2 APPLICATION OF SECTION
4.2.1 General application
Requirements of this Section shall be applied as follows:
A2
(a)
For car parks. .................................................................... Clauses 4.4 and 4.6 to 4.12.
(b)
For enclosures other than car parks ............................................... Clauses 4.5 to 4.12.
(c)
For other occupancies within car parks ................................................... Clause 4.2.2.
4.2.2 Other occupancies
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Other occupancies located within the car park area (e.g. offices, retail premises, mechanics
shops, tyre shops or similar premises), including fixed locations in the enclosure where car
park staff are located (e.g. pay booth), shall be provided with outdoor air supply that is in
accordance with Section 2, and—
(a)
sufficient to ensure the outflow of air from these areas/occupancies to be at a velocity
of not less than 0.5 m/s when doors and other openings that are normally open in the
conduct of the business of the area/occupancy are open;
(b)
outdoor supply of this area/occupancy is the greater of 30 L/s.m2 of floor area and
500 L/s; or
(c)
sufficient to ensure that the CO concentration in the area/occupancy does not exceed
30 ppm (8 h time weighted average).
A2
A2
Air supplied may (upon leaving the area or occupancy) be used as supply air to the
associated car park.
Any adjacent occupied enclosure shall be provided with supply air to maintain it at a higher
pressure than the car park. This may be achieved by providing a pressurized disconnecting
compartment, which may be supplied by the car park supply air system.
NOTE: For commentary on carbon monoxide exposure levels in occupational environments, see
Appendix H.
4.3 NOTATION
4.3.1 Symbols
The following symbols are used in this Section:
A
= the area of the zone or level, in square metres
C
= the contaminant generation rate for the zone or level, determined in accordance
with Clause 4.4.4.1
CF
= cycle factor, dimensionless (2 for 2-stroke, 4 for 4-stroke) (see Clause 4.5.3.4)
d1
= the average driving distance, in metres, within the zone or level under
consideration for the exit of a car parked there (see Clause 4.4.4.1)
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45
A1
AS 1668.2—2012
d2
= the average driving distance, in metres, within the zone or level under
consideration for the exit of a car whose exit route passes through the zone or
level under consideration, but excluding any part of the exit route designated as
queuing areas and ventilated in accordance with Clause 4.6 (see Clause 4.4.4.1)
E
= the staff exposure factor determined from Table 4.3
EL
= carbon monoxide exposure limit
EL30
= 30 ppm CO for a staffed car park
EL60
= 60 ppm CO for a non-staffed car park
FF
= fuel factor, dimensionless (1.08 to be used for petrol and heavier, e.g. diesel
fuels) (see Clause 4.5.3.4)
F
= the staff usage factor determined from Table 4.3
FVR
= full ventilation rate (see Clause 4.11.2)
L
= engine capacity, in litres (see Clause 4.5.3.4)
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MVR = minimum ventilation rate (see Clause 4.11.2)
n1
= the number of parking spaces in the zone of level under consideration (see
Clause 4.3.2)
n2
= the number of parking spaces situated in other parts of the car park, having exit
routes passing through the zone or level under consideration
nL
= number of parking spaces per exit lane
P
= the parking usage factor determined from Table 4.1
PM
= manifold pressure, in kilopascals absolute (see Clause 4.5.3.4)
PA
= atmospheric pressure, in kilopascals absolute (see Clause 4.5.3.4)
R
= engine speed, in revolutions per min (see Clause 4.5.3.4)
T
= the vehicle type factor determined from Table 4.2
TA
= engine aspiration air temperature, degrees centigrade, downstream of all
superchargers, turbochargers, intercoolers, aftercoolers and the like
(see Clause 4.5.3.4)
TE
= exhaust gas temperature, in degrees centigrade, at tailpipe (see Clause 4.5.3.4)
V
= volumetric exhaust flow rate, in litres per second (see Clause 4.5.3.4)
VE
= engine volumetric efficiency, dimensionless (0.9 to be used, unless enginespecific date is available) (see Clause 4.5.3.4)
VVR
= variable ventilation rate, in litres per second (see Clause 4.11.2)
Z
= concentration of CO, expressed as a fraction of the EL
4.3.2 Number of car spaces
The number of car parking spaces in an enclosure shall be nominated (n 1). If this
information is not shown on the design drawings, the nominated value shall be taken as one
twenty third (1/23) of floor area of the enclosure when measured in square metres,
including traffic lanes, ramps and the like, but excluding any area ventilated by other
air-handling system(s) or covered by Clause 4.5.
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AS 1668.2—2012
46
4.4 CAR PARKS
4.4.1 General
Car parks that are not adequately naturally ventilated shall be mechanically ventilated by a
combination of general exhaust with flow rates in accordance with Clause 4.4.3 or 4.4.4, as
applicable, and supply with flow rates as required to comply with Clause 4.8, subject to the
following variations:
(a)
The mechanical supply air system may be omitted, provided each zone and level of
the car park has openings directly to outside, in compliance with Clause 4.4.2.
(b)
The mechanical exhaust air system may be omitted, provided—
(i)
the floor is no more than 1.2 m below the external ground level adjacent to the
relief air openings;
(ii)
the car park has relief openings directly to the outside in compliance with
Clause 4.4.2;
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(iii) the supply airflow rate complies with Clause 4.4.3 or 4.4.4;
(iv)
the location of relief air openings, including car entries and exits, are not less
than 6 m away from any outdoor air intake or natural ventilation opening; and
(v)
any adjacent occupied enclosure is at a pressure higher than that of the car park.
C4.4.1 Using the simple procedure set out in Clause 4.4.3 will result in an equal or
higher ventilation flow rate than using the detailed procedure set out in Clause 4.4.4. In
all cases, provision of airflows in accordance with Clause 4.4.4 meets the minimum
ventilation requirement.
Maintaining positive pressure at adjacent enclosures may be accomplished by the
provision of a pressurized disconnecting compartment. Any disconnecting compartment
may be served by the car park supply system. Relief openings within 6 m of a
thoroughfare where people congregate (e.g. a bus stop) may not be acceptable.
4.4.2 Ventilation distribution
Where mechanical ventilation is provided by supply or exhaust systems, with or without
make-up air or relief-air openings, the following apply:
A2
(a)
Airflow rates at each supply air or exhaust air opening shall ensure that the quantity
of air passing across areas of the enclosure is in approximate proportion to the
number of vehicle spaces through which the air passes.
(b)
All relief-air or make-up air openings shall be sized so that the pressure difference
across the relief opening does not exceed 12 Pa.
(c)
For enclosures with exhaust ventilation, all parts of the car park shall be within 7 m
of the shortest path(s) between any exhaust-air opening and any make-up air or
supply air opening and not more than 10% of the area within the enclosure shall be
more than 3 m from the shortest path(s) between any exhaust-air opening and any
make-up air or supply-air opening.
Alternatively, the shortest path(s) between any exhaust air opening and any make-up
air or supply-air opening may be distorted through the centre-line of an additional
air-moving device such as a jet fan or high velocity supply air outlet, provided—
(i)
this device is capable of providing a horizontal thrust of not less than 5 N for
each 100 m2 of the car park area outside of the general limits imposed by
Item (c). The thrust may be calculated from the following formula:
Thrust (N) = 0.001176  flow rate (L/s)  discharge velocity (m/s)
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47
(ii)
A2
AS 1668.2—2012
the new, distorted path reverts to the shortest path between supply and exhaust
openings, from the point where the terminal velocity from the air moving
device drops below 1 m/s along a central axis in the direction of throw;
(iii) permanent obstructions and vehicle locations are not located within a zone
determined by a 15° cone on the centre-line of the airstream from the airmoving device, from the face of the discharge opening to a point where the
terminal velocity drops below 1 m/s; and
(iv)
(d)
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A2
(e)
where the air moving device is a fan, the location of the fan intake is within 7 m
of the shortest path(s) between any exhaust-air opening and any make-up air or
supply air opening. For the purposes of this clause, the shortest path shall be
assessed before locating the fan.
Where an enclosure is provided with supply air only, the following conditions apply:
(i)
All parts of the enclosure shall be within 10 m of a supply-air opening and each
supply-air opening shall serve not more than 50 m2 of area, and shall be
designed to produce a minimum terminal velocity of 0.15 m/s within the area it
serves.
(ii)
The location of any relief-air openings, including vehicle entries and exits shall
be more than 6 m away from any outside air intake or natural ventilation
opening not associated with the enclosure.
Where an additional air-moving device installed in accordance with this Standard is a
fan (such as a jet fan), these shall not be installed to operate in series.
NOTE: Example layouts complying with this Clause are shown in Appendix I.
C4.4.2 Where exhaust air intakes or any relief openings are further than 40 m away
from supply air outlet or any make-up air opening, consideration should be given to
potentially deleterious effects of short-circuiting, stack effect, wind forces and
interaction with other systems. Where the distance is greater than 75 m, the ability of
such an ‘engineered’ system to effectively dilute polluted air in all parts of the car park
should be demonstrated.
Where make-up air sources are subject to high ambient CO levels and the make-up
openings are located within 3 m of ground level, the use of supply air ventilation from
an alternative source of outdoor air may be needed.
For enclosures provided with exhaust only, or with supply only, the specified pressure
difference (12 Pa) will normally be achieved when the air velocity through relief-air or
make-up air openings does not exceed 1 m/s. For enclosures with supply only, air
openings should not be within 6 m of a thoroughfare where people congregate
(e.g. a bus stop).
A2
‘The application of this Clause covers the use of jet fans in car park ventilation systems
that have a mechanical exhaust. This Standard does not cover the use of jet fans in
naturally ventilated car parks (i.e. with no supply or exhaust fans) and the use of jet
fans in car parks that contain mechanical supply air (fans) combined with natural relief
openings.’
4.4.3 Simple procedure for small car parks
As an alternative to Clause 4.4.4, for car parks with 40 or fewer car spaces with no special
vehicle population and no attendant parking, the airflow rate, in litres per second, may be
taken as the greatest of—
(a)
400 n 1P;
. . . 4.4.3(1)
(b)
2000; or
. . . 4.4.3(2)
(c)
2.5  A.
. . . 4.4.3(3)
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AS 1668.2—2012
48
4.4.4 Detailed procedure
4.4.4.1 Contaminant generation rate
For each car park enclosure, calculate the contaminant generation rate (C), in litres used per
second, given by the following equation:
C = P  (100  n1 + n1  d 1 + n2  d2)
. . . 4.4.4.1
NOTES:
1 A distance equal to one half of the perimeter of the car park, in metres, may be used as the
value of d 1 or d 2.
2 The basis for the contaminant generation rate equation is provided in Appendix J.
4.4.4.2 Airflow rate
For car parks, the airflow rate, in litres per second, shall be calculated separately for each
zone or level, and shall be not less than the greatest of—
(a)
0.85 C  E  T;
(b)
2000  F  T; or
(c)
2.5  A.
TABLE 4.1
PARKING USAGE FACTOR
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Use of car park
Parking usage factor
(P)
Residential
0.3
Commercial
0.5
Retail/food and drink services
0.7
Entertainment/sports centres
1.0
Vehicle depots (see Note)
2.4
NOTE: This provides for areas where vehicles are left
idling for a significant period of time. In other
circumstances, a lower figure may apply.
TABLE 4.2
VEHICLE TYPE FACTOR
Types of vehicles
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Vehicle type factor
(T)
No special vehicle population
1.0
Diesel vehicles
2.4
LPG vehicles
1.0
CNG vehicles
1.0
Electric powered vehicles
0.1
Motorcycles
0.25
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49
AS 1668.2—2012
TABLE 4.3
STAFF USAGE/EXPOSURE FACTORS
Parking procedure
Staff exposure
factor (E)
Staff usage factor (F)
No special procedure (self-parking), any
staff in separate enclosure ventilated in
accordance with Clause 4.2.2
1
1
Self-parking stack parking, any staff in
separate enclosure ventilated in accordance
with Clause 4.2.2
1
1 + 0.1  No. of car spaces without
immediate access to driveway
No special procedure (self-parking), staff
located in car parking enclosure
1.8
2
Self-parking stack parking, staff located in
car parking enclosure
1.8
2 + 0.25  No. of car spaces without
immediate access to driveway
Attendant parking no stack parking
1.8
2.5  No. of attendants
Attendant parking stack parking
1.8
3.5  No. of attendants
Mechanical stack parking
1.8
2  No. of cars engines operating
at any one time
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NOTE: The staff exposure factor (E) addresses the need for lower CO concentrations if staff have an
occupational exposure. The staff usage factor (F) addresses the effect on number of engines operating
resulting from different management arrangements, combined with staff exposure considerations.
4.5 ENCLOSURES OTHER THAN CAR PARKS
4.5.1 Enclosed driveways associated with buildings
Enclosed driveways giving access to areas in buildings, including loading docks, car parks
and servicing facilities, shall be ventilated by an air-handling system. The airflow rate shall
be not less than 200 L/s per metre length of each traffic lane in excess of 20 m from the
outdoor air.
4.5.2 Loading docks
Loading docks, in which the rear of the docked vehicle may be located at a distance greater
than 10 m from the vehicle entrance opening in an external wall, shall be ventilated by an
exhaust system. The airflow rate while the dock is in use shall be not less than 1500 L/s per
vehicle docking space with a minimum of 3000 L/s.
4.5.3 Automotive service and repair shops
4.5.3.1 General
Automotive service bays, repair shops and similar premises extending more than 10 m from
natural ventilation openings shall be mechanically ventilated, unless provision is made for
directly ducting engine exhaust fumes as specified in Clause 4.5.3.2, at a flow rate being the
greater of 600 L/s per car space or 3000 L/s. Where separate provision is made to directly
duct away engine exhaust fumes, the number of parking spaces requiring ventilation may be
reduced accordingly.
4.5.3.2 Direct ducting from tailpipes
Where provisions are made for direct ducting of engine exhaust fumes to outside, the
exhaust ducts shall be designed to slip over the engine tailpipe and shall be connected to an
exhaust ventilation system having minimum exhaust airflow rates calculated in accordance
with Clause 4.5.3.3 or 4.5.3.4.
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AS 1668.2—2012
50
4.5.3.3 Direct ducting—Simple procedure
Minimum exhaust airflow rate shall be in accordance with Table 4.4.
TABLE 4.4
MINIMUM EXHAUST AIRFLOW RATES
AND DUCT DIAMETER FOR VARIOUS
TYPES OF VEHICLES
Type of vehicle
Vehicles up to 150 kW NEP*
Minimum exhaust
airflow rate per tailpipe
L/s
50
Petrol engine vehicles over 150 kW NEP
100
Diesel engine vehicles over 150 kW NEP
200
* NEP (net engine power) in accordance with Australian Design Rules
4.5.3.4 Direct ducting—Detailed procedure
The volumetric flow rate into the exhaust duct (the sum of engine tailpipe emissions and
ambient air entry into the end of the duct) shall be not less than 1.5 times the volumetric
exhaust flow from the tailpipe.
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The volumetric exhaust flow rate (V), from the tailpipe shall be determined, for
reciprocating engines, as follows:
V  L  R  1 / 60  VE  FF  2 / CF   273  TE  / 273  TA  PM / PA . . . 4.5.3.4
C4.5.3.4 The calculation applies to spark ignition engines and may be applied to
compression ignition engines (with results up to approximately 8% conservative). The
fuel factor [volumetric ratio of exhaust products, in litres per second, to aspirated air,
in litres per second, both at standard temperature pressure (STP)] may be as high as
1.21 for hydrogen or methanol; the value for hydrocarbon fuels is generally lower than
this. Engine volumetric efficiency may be expressed as a function of manifold pressure
and revolutions per minute (rpm), 0.5 to 0.9 is a reasonable range for a spark ignition
engine. Manifold pressure (generally, atmospheric pressure minus engine vacuum) is
depressed below atmospheric pressure by aspiration air path pressure losses. Manifold
pressure may be increased above atmospheric pressure by operation of superchargers
and turbochargers. For naturally aspirated engines with minimally heated intake air
path, TA may be taken as the ambient air temperature. Exhaust gas temperature, though
engine specific, may typically be in the range of 400°C to 1100°C at manifold
(increasing with speed and load) for spark ignition engines at stable operating
temperature. Exhaust gas temperatures, though engine specific, may typically be in the
range of 350°C to 650°C at manifold (increasing with load) for compression ignition
engines at stable operating temperature.
4.5.3.5 Dynamometer engine testing
Where dynamometer engine testing facilities are incorporated, each bay shall either—
(a)
have engine exhausts directly ducted away at a rate calculated in accordance with
Clause 4.5.3.4; or
(b)
be provided with a general exhaust system extracting not less than 3000 L/s per bay.
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AS 1668.2—2012
4.5.4 Vehicular lifts and shafts
4.5.4.1 Exhaust ventilation of vehicular lift cars
Lifts
shall
open
shaft
used for transporting vehicles within a building shall be ventilated. The airflow rate
be not less than 2000 L/s to allow for undisturbed airflow through the lift. Lifts with
sides and no ceiling may be exempted from the exhaust requirement, provided the lift
complies with Clause 4.5.4.2.
4.5.4.2 Exhaust ventilation of vehicular lift shafts
Vehicular lift shafts shall be ventilated by a mechanical air-handling system at a flow rate
of not less than 2000 L/s.
4.5.5 Areas used by special purpose vehicles
Areas within buildings, where special purpose vehicles (e.g. forklift trucks) operate, shall
be ventilated. The ventilation airflow rates given in Table 4.5 shall apply. Make-up air or
relief air shall be provided by means of uniformly distributed natural ventilation openings
or a mechanical air-handling system. The vehicle engines shall not exceed 45 kW.
Where the above conditions are not met, the flow rates in Table 4.5 shall be adjusted
proportionally.
NOTE: A sign should be displayed in a conspicuous position, stating the maximum number of
vehicles that may be operated in order to keep emissions within design levels.
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TABLE 4.5
EXHAUST AIRFLOW RATES FOR AREAS
USED BY SPECIAL PURPOSE VEHICLES
Fuel used by vehicle
Minimum airflow rate
Liquefied petroleum gas
2500 L/s per vehicle
Diesel oil
2500 L/s per vehicle
Petrol
4000 L/s per vehicle
4.6 QUEUING AREAS
4.6.1 General
Enclosures where vehicles queue up with engines operating for any purpose, including
parcel pick up, purchasing, payment at exits or awaiting entry or exit, shall be mechanically
ventilated in accordance with Clauses 4.6.2 and 4.6.3 unless naturally ventilated.
4.6.2 Queuing length
The length of a queue shall be stated by the owner of the building.
NOTE: For guidance on determining queue lengths, see Tables 4.6 and 4.7.
C4.6.2 Several factors influence the length of queues, including use of the enclosure,
number and location of entry and exit points and external traffic conditions. Car parks
associated with entertainment and sporting venues tend to have longer queues than
other car parks.
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AS 1668.2—2012
52
TABLE 4.6
LENGTH OF QUEUES AT ENTRY POINTS
Type of entry
Queuing length
Barrier or ticket dispensing
Full length of entry lane up to barrier
Unhindered
Nil
TABLE 4.7
LENGTH OF QUEUES AT EXIT POINTS
Traffic conditions in
street at exit
Queuing length
m
Barrier or checkpoint
Any
2.2n LP  200
Unhindered
(i.e. free or central payout)
Light
2.2n LP  400
Heavy
2.2n LP  200
Type of exit
4.6.3 Airflow rate and distribution of air
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The exhaust airflow rate shall be—
(a)
225 L/s per metre length of each exit lane queue; and
(b)
150 L/s per metre length of each entry lane queue.
The location and distribution of exhaust air intakes and source of make-up air as well as
airflow rates at each exhaust air intake shall be such that air passing across the queuing area
is uniformly distributed for its full length.
NOTE: The derivation of airflow rates for queuing areas are provided in Appendices K and L.
4.7 AIR PRESSURE
Air pressure in an enclosure ventilated by an exhaust air system shall comply with
Clause 3.7.2.
4.8 MAKE-UP OF EXHAUST AIR
The make-up of exhaust air shall be in accordance with Clause 3.8. Where a supply
ventilation system for make-up air is provided, it shall have a flow rate of not less than 75%
and not more than 90% of the exhaust airflow rate.
4.9 EXHAUST AIR DISCHARGE
Exhaust air discharge shall be in accordance with Clause 3.10.2.
A2
NOTE: Exhaust air discharge is not considered objectionable.
4.10 COMBINATION SYSTEMS
Where a combination of natural and mechanical ventilation systems are used, the systems
shall be considered separately. Air from a naturally ventilated portion shall not be used as
make-up air for the mechanically exhausted portion.
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53
AS 1668.2—2012
4.11 VENTILATION CONTROL
4.11.1 General
A2
Ventilation systems shall operate at all times, at the full ventilation rate (FVR), calculated
in accordance with Clause 4.4 and/or Clause 4.5, unless the ventilation systems are
controlled in accordance with Clause 4.11.2 or 4.11.3.
A car park ventilation system shall operate to provide at least 1 air change in every 24 h
period.
4.11.2 System operation
Systems shall be controlled by an atmospheric contaminant monitoring system in
accordance with Clause 4.12. In this application, ventilation rates shall be varied such that
when the concentration of contaminants measured by any sensor within the enclosure are in
accordance with the following:
(a)
At 75% of the carbon monoxide exposure limit (EL) and above The system shall
provide not less than the FVR.
(b)
Between 50% and 75% of the EL The system shall provide not less than the variable
ventilation rate (VVR) calculated in accordance with the following equation:
 Z  0.5 
VVR  MVR  
  FVR  MVR 
 0.25 
. . . 4.11.2
(c)
Below 50% of EL The system shall provide not less than the minimum ventilation
rate (MVR) = 25% of FVR.
(d)
Below 25% of EL Intermittent ventilation shall be allowed.
NOTE: The system may turn OFF below 15% of EL and restart again at MVR when 25% of
EL is reached.
NOTES:
1 At the time of publication, EL is EL 30 at 30 ppm CO for a staffed car park and EL 60 at 60 ppm
CO for a non-staffed car park. Z is the fraction of the EL measured at the sampling point,
expressed as a decimal.
2 Figure 4.2 provides a graphical representation of the control method required by
Clause 4.11.2.
10 0%
Ventilation of 1 air change per 24 h to be incorporated
75%
50%
O FF
ON
%F V R
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A1
25%
Inte r m i t te nt o p e r ati o n
p e r m i t te d i n thi s zo n e
0%
0%
0
0
15%
9
5
25%
15
7
50%
30
15
75%
45
23
10 0%
%EL
60
EL 6 0 = 6 0 p p m
30
EL 3 0 = 3 0 p p m
FIGURE 4.2 VENTILATION CONTROL
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AS 1668.2—2012
54
4.11.3 Small car parks
For car parks with 40 or fewer car spaces, ventilation systems shall operate at all times, at
the FVR, calculated in accordance with Clause 4.4; however, the following energy-saving
measures are permitted:
A2
(a)
Operation in accordance with Clause 4.11.2.
(b)
Where all vehicles remain parked with engines not operating for periods in excess of
2 h, the prescribed appropriate airflow rate is permitted to be halved during such
periods.
(c)
Where all vehicles remain parked with engines not operating and the space is
unoccupied for periods in excess of 2 h, shutdown of the system is permitted.
Provision shall be made to automatically restart the system at a flow rate not less than 50%
of FVR should the space become occupied. In these cases of automatic restart, the car park
ventilation systems shall operate for not less than 10 min after the enclosure is no longer
occupied.
C4.11.3 Items (b) and (c) Acceptable methods for automatic restart of ventilation
systems include activation by motion detectors adjacent to all doorways and all lift
doors providing access to the car park, plus automatic activation whenever the vehicle
entrance door(s) are opened.
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4.11.4 Make-up air
Make-up air for each zone or level shall be maintained in accordance with Clause 4.8 to suit
minimum, maximum and all intermediate ventilation rates of the mechanical ventilation
systems.
4.12 MONITORING OF ATMOSPHERIC CONTAMINANTS
4.12.1 General
Where the operation of mechanical ventilation is automatically controlled by an
atmospheric contaminant monitoring system(s), the calculated air quantity is permitted to
be varied, subject to the requirements of this Clause and Clause 4.11. The atmospheric
contaminant to be monitored shall be CO.
C4.12.1 Advice from health authorities indicate that monitoring of CO is optimum for
contaminant monitoring systems for enclosures used by vehicles with combustion
engines. Although NO2 is produced by some combustion engines, monitoring results
have indicated that CO levels exceed the exposure standard (ES) before NO2 levels.
4.12.2 System requirements
A CO monitoring system that is installed to regulate mechanical ventilation shall—
(a)
be provided with display to indicate the current instantaneous concentration;
(b)
operate 24 h per day;
(c)
under any fault condition, activate an alarm and operate the ventilation system at the
full ventilation rate (FVR);
(d)
be clearly marked to indicate servicing and calibration requirements in accordance
with Clause 4.12.6; and
(e)
analyse the air—
(i)
at all sampling points continuously, and simultaneously and automatically
operate the mechanical ventilation system in accordance with Clause 4.11.2; or
(ii)
from all sampling points intermittently, at least twice every 4 min and
automatically operate the mechanical ventilation in accordance with
Clause 4.11.2.
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55
AS 1668.2—2012
C4.12.2 This Standard permits CO monitoring systems that incorporate sampling and
detection devices that analyse the air at sampling points and transmit signals to a
central reporting station as well as CO monitoring systems that draw samples of air
from sampling points to a central analyser that transmits signals to a central reporting
station.
4.12.3 Operation and accuracy of CO monitors
The monitoring system shall be selected to measure the concentration of CO to within 10%
of the exposure limit (EL) for measurements in the range between 10% and 120% of the EL,
and to within 10% of the full range deflection of the monitoring system for measurements
over 120% of the EL.
C4.12.3 The exposure limit is set by NOHSC, NHMRC or NEPC, as applicable. For
more commentary on carbon monoxide exposure in occupational environments, see
Appendix H.
4.12.4 Analysis of CO response time of monitoring systems
When a system detects an increase in CO above a set point, reaction of the system to the
increase above the value calculated in accordance with Clause 4.11.2 shall be immediate
after the increase has been sustained for 5 min or detected on consecutive analyses of the
same sampling point for a period not longer than 5 min.
4.12.5 Sampling points
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4.12.5.1 Location and number
Sampling points shall be located—
(a)
so that no point in the enclosure is greater than 25 m away from a sampling point;
(b)
between 750 mm and 1800 mm above the floor surface in positions that will allow
samples to be fully representative of the local atmosphere; and
(c)
as far as is practicable, situated closer to exhaust inlets than make-up air outlets and
situated so that the distance from exhaust openings is 3/10 of the distance between
make-up air and exhaust-air openings; and
NOTE: Depending on the car park geometry, this may require additional detectors than
required by Item (a) alone.
(d)
additional detectors shall be provided in areas where people congregate, such as
waiting areas for drivers or passengers of motor vehicles that are not within
separately ventilated areas.
4.12.5.2 Enclosure area
Where the enclosure does not consist of one regular area, each more or less regular area
shall be treated as one enclosure.
4.12.6 Marking, commissioning, reliability and records
In order to ensure the extended reliability of monitoring systems and the evidence of that
reliability, service markings shall be provided and records shall be kept.
NOTE: For automatic monitoring systems for car parks, see Appendix M.
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 Standards Australia
AS 1668.2—2012
56
SECTI ON 5
MECHANICAL VENTI LATION
ENCL OSUR ES US ED FOR PAR TICUL AR
HEAL TH CARE FUNCTIONS
OF
5.1 SCOPE OF SECTION
This Section sets out requirements for the mechanical ventilation of particular types of
health care enclosures, which differ from those of other mechanically ventilated enclosures.
These particular enclosures are conventionally known as operating rooms, sterile stores/
set-up rooms, isolation rooms, recovery rooms, autopsy rooms and dirty utility rooms.
NOTE: The need for the segregation of systems serving operating rooms should be assessed on a
case by case basis.
5.2 APPLICATION OF SECTION
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Requirements of this Section apply to the minimum mechanical ventilation requirements for
particular types of health care enclosures, as follows:
(a)
For operating rooms, Clause 5.3 shall apply.
(b)
For sterile store and set-up rooms, Clause 5.4 shall apply.
(c)
For infectious isolation rooms, Clause 5.5 shall apply.
(d)
For protective isolation rooms, Clause 5.6 shall apply.
(e)
For recovery rooms, Clause 5.7 shall apply.
(f)
For autopsy rooms, Clause 5.8 shall apply.
(g)
For dirty utility rooms, Clause 5.9 shall apply.
NOTE: A flow chart on the application of this Section is given in Figure 5.1.
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 Standards Australia
57
AS 1668.2—2012
S ECT I O N
5
I s th e e n c l o s u r e
a n o p e r ati n g
r o o m?
Comply
with
Clau se 5. 3
C a l c u l a te m i n i m u m
a i r c h a n g e r ate
Clau se 5. 3. 2
Ye s
Comply
with
Clau se 5.4
C a l c u l a te m i n i m u m
a i r f l ow r ate
Clau se 5.4. 2
Ye s
C o m p l y wi th
Cl a u s e 5. 5 o r 5.6
a s a p p r o p r i ate
C a l c u l a te m i n i m u m
o u td o o r a i r r ate
Cl a u s e 5. 5. 3 o r
5.6.4
Ye s
C o m p l y wi th
Clau se 5.7
Ca l c ul ate ex h a u s t
a i r r ate
Clau se 5.7. 3
Ye s
C o m p l y wi th
Clause 5.8
Ca l c ul ate ex h a u s t
a i r r ate
Clause 5.8.3
Ye s
C o m p l y wi th
Clause 5.9
Ca l c ul ate ex h a u s t
a i r r ate
C l a u s e 5 . 9. 3
Ye s
C a l c u l a te m i n i m u m
o u td o o r a i r r ate
Clau s e 5. 3.4
No
Is enclosure
a s te r il e s to r e o r
s e t- u p r o o m?
No
Is enclosure an
i s o l ati o n
r o o m?
C a l c u l a te m i n i m u m
s u p p l y a i r r ate
Clau s e 5.6. 2
No
Is enclosure a
r e c ove r y
r o o m?
No
Is enclosure an
a u to p sy
r o o m?
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No
Is enclosure a
dir ty utility
r o o m?
Refe r
f il tr ati o n
requirement
I n s t a ll r e q u i r e d
f il te r s a n d c h e c k
room air pressure
Refe r
p r e s s u r iz ati o n
requirement
EN D
FIGURE 5.1 GUIDANCE ON THE APPLICATION OF SECTION 5
5.3 OPERATING ROOMS
5.3.1 General
Operating rooms shall be mechanically ventilated in accordance with Clauses 5.3.2 to 5.3.7.
5.3.2 Air change rate
The supply air rate shall be not less than that calculated to achieve 20 air changes per hour
in the operating room.
5.3.3 Recirculation
A2
Air supplied to operating theatres, anaesthetic bays, sterile stores and set-up rooms shall not
be recirculated from any other enclosure type.
5.3.4 Outdoor air rate
The minimum outdoor airflow rate shall be the greater of 20 L/s per person at an occupancy
of 5 m2 per person, or 10 air changes per hour.
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AS 1668.2—2012
58
5.3.5 Supply air filtration
The supply air shall be filtered, using high efficiency particulate air (HEPA) filters in
accordance with AS 4260 Type 1 Class A Grade 2 with a minimum efficiency of 99.99%.
HEPA filters shall be located in a terminal position; that is, they shall be close to or at the
supply air register in the operating room.
5.3.6 Recycle and exhaust grille location
Recycle and exhaust air shall be drawn from the room via grilles with not less than 50% of
the minimum outdoor air being drawn through low level grilles, the bottom of which shall
be not more than 300 mm above floor level.
5.3.7 Room air pressure
The air pressure within the operating room shall be maintained above that in adjacent
enclosures, other than sterile store and set-up rooms (which are required to have a room air
pressure greater than that in the operating room).
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Pressure differentials across doors shall be such that—
(a)
the force to open any door against the combined effect of the air pressure differential
and any self-closing mechanism does not exceed 110 N at the door handle; and
(b)
doors are not prevented from closing and latching, that is, the force due to air
pressure on the door leaf does not exceed the force of the self-closing or automaticclosing device and latching device.
5.4 STERILE STORE AND SET-UP ROOMS
5.4.1 General
A2
Anaesthetic bays, sterile stores and set-up rooms shall be mechanically ventilated in
accordance with Clauses 5.4.2 to 5.4.4.
5.4.2 Outdoor air rate
A2
The minimum outdoor airflow rate delivered to the anaesthetic bays, sterile store and set-up
rooms isolation room shall be the greater of 10 L/s per person and 2 L/s.m2.
Air supplied to anaesthetic bays, sterile store and set-up rooms and operating rooms shall
not be recirculated from any other enclosure type.
5.4.3 Recirculation
Air supplied to operating theatres, anaesthetic bays, sterile stores and set-up rooms shall not
be recirculated from any other enclosure type.
5.4.4 Room air pressure
A2
The air pressure within the sterile store and set-up enclosures shall be maintained higher
than that in adjacent enclosures. HEPA filters shall be located in a terminal position; that is,
they shall be close to or at the supply air register in the anaesthetic bays, sterile store or
set-up room.
5.5 INFECTIOUS ISOLATION ROOMS
5.5.1 General
Infectious isolation rooms shall be mechanically ventilated in accordance with
Clauses 5.5.2 to 5.5.5.
NOTE: For additional information on infection isolation, see HB 260.
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AS 1668.2—2012
5.5.2 Recirculation
Air shall not be recirculated from infectious isolation rooms to any other enclosure.
5.5.3 Outdoor air rate
The minimum outdoor airflow rate delivered to the infectious isolation room shall be the
greater of 10 L/s per person and 2 L/s.m2.
5.5.4 Exhaust air rate
Infectious isolation rooms shall be mechanically exhausted to atmosphere as a Type A
effluent, at a rate not less than six air changes per hour.
NOTE: Filtering of exhaust air may be necessary.
5.5.5 Room air pressure
Infectious isolation rooms (for example, isolation rooms used to isolate patients suffering
from ‘droplet infection’ diseases) shall have controlled room air pressure that is lower than
that of adjacent enclosures. The differential pressure between the isolation room and
adjacent enclosures shall be automatically controlled and shall comply with the door
opening limitations of Clause 5.3.7.
5.6 PROTECTIVE ISOLATION ROOMS
5.6.1 General
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Protective isolation rooms shall be mechanically ventilated in accordance with
Clauses 5.6.2 to 5.6.5.
NOTE: For additional information on protective isolation, see HB 260.
5.6.2 Supply air rate
Supply air shall be delivered to a protective isolation room to provide not less than 15 air
changes per hour.
5.6.3 Recirculation
Supply air delivered to a protective isolation room shall not be recirculated to any other
room (indirect recirculation of air leaked from the positively pressurized room is
acknowledged) unless the air has been filtered using HEPA filters in accordance with
AS 4260 Type 1 Class A Grade 2 with a minimum efficiency of 99.99%.
5.6.4 Outdoor air rate
The minimum outdoor airflow rate delivered to the isolation room shall be the greater of
10 L/s per person and 2 L/s.m2.
5.6.5 Room air pressure
Protective isolation rooms that are used to isolate patients shall have controlled room air
pressure that is higher than that of adjacent enclosures. The differential pressure between
the isolation room and adjacent enclosures shall be automatically controlled and shall
comply with the door opening limitations of Clause 5.3.7.
A2
5.7 POST ANAESTHETIC CARE UNIT (PACU) (Recovery Stage 1)
5.7.1 General
A2
Post anaesthetic care rooms shall be mechanically ventilated in accordance with
Clauses 5.7.2 and 5.7.3.
C5.7.1 The exhalation of anaesthetic gases by patients may present a hazard in
inadequately ventilated recovery rooms.
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AS 1668.2—2012
60
5.7.2 Recirculation
A2
Air shall not be recirculated from the post anaesthetic care room to any other enclosure.
5.7.3 Exhaust air rate
A2
Post anaesthetic care rooms shall be mechanically exhausted to atmosphere at a minimum
airflow rate of the greater of 10 L/s per person and 4 L/s.m2.
5.8 AUTOPSY ROOMS
5.8.1 General
Autopsy rooms shall be mechanically ventilated in accordance with Clauses 5.8.2 to 5.8.4.
5.8.2 Recirculation
Air shall not be recirculated from the autopsy room to any other enclosure.
5.8.3 Exhaust air rate
Air shall be exhausted from the enclosure at a rate of not less than 12 air changes per hour.
5.8.4 Exhaust location
Exhaust air shall be drawn from the room via grilles, not less than 50% of the exhaust air
being drawn through low level grilles, the bottom of which shall be not more than 300 mm
above floor level and discharged to atmosphere as a Type A effluent (see Section 3).
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5.8.5 Room air pressure
The air pressure within the autopsy room shall be less than that in adjacent enclosures.
Pressure differentials shall comply with the door opening limitations of Clause 5.3.7.
5.9 DIRTY UTILITY ROOMS
5.9.1 General
Dirty utility rooms are enclosures in which contaminated linen, utensils and instruments are
located in preparation for cleaning. Dirty utility rooms shall be mechanically ventilated in
accordance with Clauses 5.9.2 and 5.9.4.
5.9.2 Recirculation
Air shall not be recirculated from the dirty utility room to any other enclosure.
5.9.3 Exhaust air rate
The mechanical exhaust rate shall be sufficient to provide not less than 10 air changes per
hour.
5.9.4 Room air pressure
The air pressure within dirty utility rooms shall be less than that in adjacent enclosures
achieved by the mechanical exhaust system. Pressure differentials shall comply with the
door opening limitations of Clause 5.3.7.
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 Standards Australia
61
AS 1668.2—2012
APPENDIX A
MINIMUM EFFECTIVE OUTDOOR AIRFLOW REQUIREMENTS BASED ON
OCCUPANCY
(Normative)
This Appendix provides the minimum outdoor airflow rates as required by Section 2.
For enclosure types listed in Table A1, corresponding minimum per person, or per unit area
outdoor airflow rates, shall apply.
TABLE A1
MINIMUM EFFECTIVE OUTDOOR AIRFLOW RATES (q f)
A2
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Occupancy*
Net floor
area per
person
(Note 1)
m2
Minimum outdoor airflow rate
Quantity
Unit
Comments
Amusement centres
See sports centres
Beverage services
See food services
Colleges
See education
Correction centres
See prisons
Dormitories
See hotels
Dry cleaners and
laundries
More air may be required to laundries
to satisfy exhaust air requirements
Commercial
10
10
L/s.person
Coin-operated dry
cleaning
5
10
L/s.person
Coin-operated laundries
5
10
L/s.person
Pick-up areas
3.5
10
L/s.person
Storage areas
3.5
10
L/s.person
Classrooms serving
persons up to 16 years
of age
2
12
L/s.person
Classrooms serving
persons over 16 years
of age
2
10
L/s.person
Laboratories
3.5
10
L/s.person
Libraries
5
10
L/s.person
Lounges
1.5
10
L/s.person
Music rooms
2
10
L/s.person
Training shops
3.5
10
L/s.person
Education
Special contaminant control systems
may be required for processes or
functions including laboratory animal
occupancy
(continued)
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 Standards Australia
AS 1668.2—2012
62
TABLE A1 (continued)
Occupancy*
Net floor
area per
person
(Note 1)
m2
Minimum outdoor airflow rate
Quantity
Unit
Comments
Food and drink
services
Bars
1
10
L/s.person
Cabarets
1.5
10
L/s.person
Cafeterias
1
10
L/s.person
Cocktail lounges
1
10
L/s.person
Dining rooms
1.5
10
L/s.person
Fast food outlets
1
10
L/s.person
Food preparation,
serving and storage
3.5
10
L/s.person
Chapels
0.6
10
L/s.person
Embalming rooms
5
15
L/s.person
Reception rooms
1
10
L/s.person
1
L/s.m2 floor
10
L/s.person
Foyers
1
L/s.m2 floor
Lobbies
1
L/s.m2 floor
Pedestrian tunnels
1
L/s.m2 floor
Ramps
1
L/s.m2 floor
10
L/s.person
Stairs
1
L/s.m2 floor
Utility rooms
1
L/s.m2 floor
For cooking, see Section 3
Funeral parlours
Air shall not be recirculated into
spaces
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General areas
Corridors
Dressing rooms
Rest rooms
2
1
Health care
General requirements (applies to all
forms unless separately listed)
For stairs, passageways, etc. used as a
means of egress, see AS/NZS 1668.1
Applies to convalescent homes, dental
surgeries, doctors’ clinics, hospitals,
nursing homes, etc. Special
requirements or codes and pressure
relationships may determine minimum
ventilation rates and filter efficiency.
Procedures generating contaminants
may require higher rates, laminar flow
or dedicated systems
Refer also to the requirements of
Section 5
Amphitheatres
Autopsy rooms
0.6
10
L/s.person
5
L/s.m2 floor
Air shall not be recirculated
Excludes teaching spaces, which may
be subject to other regulatory
requirements
(continued)
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 Standards Australia
63
AS 1668.2—2012
TABLE A1 (continued)
Occupancy*
Net floor
area per
person
(Note 1)
m2
Minimum outdoor airflow rate
Quantity
Unit
Consultation rooms
3.5
10
L/s.person
Delivery rooms
5
20
L/s.person
Intensive care rooms
5
10
L/s.person
Operating rooms
5
20
L/s.person
10
10
L/s.person
5
10
L/s.person
10
10
L/s.person
Ready rooms
5
10
L/s.person
Recovery rooms
5
10
L/s.person
Waiting areas
1.5
10
L/s.person
1
10
L/s.person
Bedrooms (single,
double)
10
10
L/s.person
Conference rooms
(small)
2
10
L/s.person
10
L/s.person
Patient rooms
Physical therapy area
Procedure areas
Comments
Ventilation strategy must consider
exhalation of anaesthetic gases. Refer
to Section 5
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Hotels, motels, resorts
Assembly rooms (large)
Dormitories
Gambling casinos
1.5
10
L/s.person
Living rooms (suites)
5
10
L/s.person
Lobbies
3.5
10
L/s.person
Laundries
See dry cleaners
Merchandising
General requirements (apply to all
forms unless separately listed)
Arcades
5
10
L/s.person
10
10
L/s.person
Fitting rooms or
enclosures
1
10
L/s.person
Kiosks
1
10
L/s.person
Malls
5
10
L/s.person
10
10
L/s.person
Dispatch areas
Receiving areas
Sales floors or
showrooms
Basement and street
floors
3.5
10
L/s.person
Upper floors
5
10
L/s.person
10
L/s.person
Supermarkets
Sales floor area excluding display and
storage
(continued)
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 Standards Australia
AS 1668.2—2012
64
TABLE A1 (continued)
Occupancy*
Net floor
area per
person
(Note 1)
m2
Minimum outdoor airflow rate
Quantity
Unit
Storage areas (serving
sales and storerooms)
10
10
L/s.person
Warehouses
20
10
L/s.person
Motels
Comments
See hotels
Museums
Exhibits halls
10
L/s.person
20
10
L/s.person
Art rooms
5
10
L/s.person
Board rooms
1
10
L/s.person
Committee rooms
1
10
L/s.person
Computer rooms
25
10
L/s.person
Conference rooms
1
10
L/s.person
Drafting rooms
5
10
L/s.person
10
10
L/s.person
2
10
L/s.person
Cell blocks
5
10
L/s.person
Eating halls
1.5
10
L/s.person
Guard stations
2.5
10
L/s.person
Warehouses
1.5
Offices
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Office areas
Waiting areas
Prisons
Residential
Private dwellings
Private dwelling places, multiple or
single, high or low rise
Bedrooms
10
10
L/s.person
Living areas and
general
10
10
L/s.person
Other dwellings
Boarding houses
See hotels
Guest houses
See hotels
Hostels
See hotels
Mobile homes
5
10
L/s.person
Resorts
See hotels
Schools
See education
Speciality services
Animal rooms
5
L/s.m2 floor
Barber shops
4
10
L/s.person
Beauty salons
4
10
L/s.person
Broadcasting studios
1.5
10
L/s.person
(continued)
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 Standards Australia
65
AS 1668.2—2012
TABLE A1 (continued)
Occupancy*
Net floor
area per
person
(Note 1)
m2
Quantity
Unit
4
L/s.m2 floor
5
10
L/s.person
10
10
L/s.person
Greenhouses
100
10
L/s.person
Hairdressers
4
15
L/s.person
Health spas
5
10
L/s.person
PABX rooms
4
L/s.m2 floor
Pet shops
5
L/s.m2 floor
Electrical meter, switch
rooms
Exercise rooms
Florist
Press booths, lounges
1.5
10
L/s.person
Radio booths
1.5
10
L/s.person
Reducing salons
5
10
L/s.person
10
10
L/s.person
Survival shelters
1
10
L/s.person
Telephone main
distribution frame
(MDF) rooms
10
10
L/s.person
10
L/s.person
Shoe repair shops
(combined workrooms
trade areas)
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Minimum outdoor airflow rate
Television booths
1.5
Sports and
amusement centres
A2
Comments
When internal combustion engines are
operated for maintenance of playing
surfaces, or any other purpose,
exhaust ventilation may be required
Ballrooms
1.5
15
L/s.person
Bowling alleys
(seating areas)
1.5
15
L/s.person
Brothels
5
10
L/s.person
Night clubs
1.0
15
L/s.person
Games rooms
1.5
15
L/s.person
Amusement machines, billiards, cards,
etc.
Playing floors
3.5
10
L/s.person
Cricket, gymnasiums, ice skating,
roller skating, squash, tennis, etc.
Spectator areas
(general)
0.6
10
L/s.person
Swimming pools, deck
and pool area
3.5
10
L/s.person
Spectator areas (pool)
1.5
10
L/s.person
Places of worship
Higher values may be required for
humidity control
See theatres
Theatres
Auditoriums
0.6
10
L/s.person
Concert halls
0.6
10
L/s.person
(continued)
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 Standards Australia
AS 1668.2—2012
66
TABLE A1 (continued)
Occupancy*
Net floor
area per
person
(Note 1)
m2
Minimum outdoor airflow rate
Quantity
Unit
Foyers
0.6
10
L/s.person
Green rooms
5
10
L/s.person
Lecture halls
0.6
10
L/s.person
Lobbies
0.96
10
L/s.person
Opera halls
0.6
10
L/s.person
Stages
1.5
10
L/s.person
Studios
1.5
10
L/s.person
10
L/s.person
Ticket booths
Comments
Special ventilation will be needed to
eliminate special effects (e.g. dry ice
vapours, mists, etc. used in television,
film, and radio productions)
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Transportation
centres
Baggage areas
1.5
10
L/s.person
Concourses
0.6
10
L/s.person
Corridors
1.5
10
L/s.person
Gate areas
1.5
10
L/s.person
Hangars
50
10
L/s.person
Platforms
0.6
10
L/s.person
Ticket areas
1.5
10
L/s.person
Waiting rooms
1.5
10
L/s.person
Air traffic control
2
20
L/s.person
Kennels
5
L/s.m2 floor
Operating rooms
5
L/s.m2 floor
Reception rooms
5
L/s.m2 floor
Stalls
5
L/s.m2 floor
Minimum 5 L/s.m2
Refer also to aviation
standards
Veterinary centres
A2
Workrooms
This requirement covers continuous
occupancy. When occupancy is
intermittent, infiltration will normally
be sufficient ventilation.
Industrial process based
on activity level
15
L/s.person
General requirements processes (apply
to all forms unless separately listed).
High activity level
15
L/s.person
Mining, foundry, etc.
Medium activity level
10
L/s.person
Automotive repair, assembly line, etc.
10
L/s.person
Laboratory work, light assembly, etc.
This requirement covers low
temperature (23°C to 10°C) rooms
occupied continuously. Where
occupancy is intermittent, infiltration
will normally be sufficient ventilation.
Low activity level
10
(continued)
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 Standards Australia
67
AS 1668.2—2012
TABLE A1 (continued)
Occupancy*
A2
Bank vaults
Meat processing
Net floor
area per
person
(Note 1)
m2
Minimum outdoor airflow rate
Quantity
Unit
Comments
10
10
L/s.person
Emergency provisions may be needed.
5
10
L/s.person
10
10
L/s.person
Camera
rooms
10
L/s.person
Dark rooms
10
L/s.person
10
L/s.person
Pharmacists
Photography
Duplicating rooms
3.5
Installed equipment may require
exhaust, to control contaminants.
Contaminants from specialist
chemicals may require additional
ventilation.
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Printing rooms
Refrigerated rooms
Same as meat processing.
Strongrooms
Same as bank vaults.
Voucher storerooms
Same as bank vaults.
* Where an occupancy type is only listed under one building type, the values given apply to that type of
occupancy in all building types.
NOTES:
1
This column applies where the number of occupants is not known. Where the occupancy is not
indicated, the actual occupancy shall be determined during the design of the room.
2
Occupancy types listed are typical. Omission of an applicable occupancy from the Table does not
obviate the need to comply in principle with this Standard (see Clause 2.1).
3
The values of ‘net floor area per person’ are approximate.
4
The requirements for ventilation air given in these Tables represent the minimum conditions. Values
higher than the above are sometimes recommended, taking into account the required environmental
performance, and the effects of various contaminants on the health and welfare of the occupants.
5
The tabulated values are a consensus judgement of appropriate minima to reduce odours to levels
acceptable to the community. These are considerably in excess of the quantities required to ensure
healthy breathing or maintain acceptable levels of oxygen, carbon dioxide, etc. Where normally bathed,
cleanly clothed, relatively sedentary occupants are expected, the minima are appropriate. Where
unusual occupation or hygiene is expected, some appropriate increases should be made.
6
In some cases, the area per person is different than existing regulation requirements for determination
of exits, etc., since ventilation needs are based on a time-integrated requirement.
7
This Standard assumes a ventilation effectiveness of 0.8 for the minimum ventilation requirements
specified.
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 Standards Australia
AS 1668.2—2012
68
APPENDIX B
MINIMUM MECHANICAL EXHAUST AIR REQUIREMENTS BASED ON USE
OF ENCLOSURE
(Normative)
B1 APPLICATION
This Appendix provides the minimum exhaust air based on use of enclosure, as required by
Section 3.
B2 GENERAL EXHAUST FOR ENCLOSURES
Exhaust for enclosures shall be in accordance with Table B1. The exhaust rates shown are
minimum values.
TABLE B1
MINIMUM EXHAUST VENTILATION FLOW RATES
Enclosure type
Quantity
Unit
Automotive vehicle
See Section 4
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Battery charging
Change room
A2
Document copying process that emits
objectionable effluent
Drycleaning (solvent)
Comments
See AS 2676.2
5
L/s.m2
floor
May include lockers
5
L/s.m2
floor
Does not include office based
printing
20
L/s.m2 floor
Garages
See Section 4
Garbage room and service compartment
5
L/s.m2
Gas meter
5
L/s.m2 floor
Grease arrester
5
L/s.m2 floor
Autopsy
12
Air changes per
hour
Dirty utility
10
Air changes per
hour
6
Air changes per
hour
Recovery
10
Air changes per
hour
Post Anaesthetic Care Unit (PACU)
(Recovery Stage 1)
10
L/s.person
4
L/s.m2
20
L/s.m2 floor
5
L/s.m2 floor
15
L/s.m2 floor
floor
100 L/s min.
100 L/s min.
Health care
Infectious isolation
A2
Sterilizing
May be 5 L/s.m2 of floor when
local exhaust provided over
sterilizers (see Clause 3.2).
Kitchen
Commercial
Laundry
Commercial
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 Standards Australia
69
AS 1668.2—2012
TABLE B1 (continued)
Enclosure type
Quantity
Unit
Comments
(continued)
Laundry
Residential
Rate is independent of enclosure
size. Operation of the system
may be intermittent
Where a laundry is located
within a bathroom, the greater
quantity of either space shall
apply
No dryer
20
L/s.room
Condensing dryer
20
L/s.room
The greater of 110% of the
dryer airflow (where this is
known) or 20 L/s room.
Non-condensing dryer
40
L/s.room
The greater of 110% of the
dryer airflow (where this is
known) or 40 L/s room.
Sanitary compartment
A2
Bath
Shower
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Urinal
10
or
25
L/s.m2
floor
L/s per listed
fixture
Water closet
The greater of the two values
shall be taken. Each 0.6 m length
of urinal shall be considered to
be equivalent to one fitting.
Where the number of fixtures is
not known, it may be determined
at a rate of 0.4 fixtures per m2 of
floor area.
Sanitary compartments subject to
high level of use (e.g. airports,
entertainment venues, and
similar venues may require an
increased ventilation rate)
Where privacy locks or airlocks
are included, provision should be
made for their ventilation at
5 L/s.m2 of floor area (e.g. via
make-up air)
(Handbasins are not considered
as a ‘listed fixture’)
Bathroom/Toilet
25
L/s/room
Private dwellings and attached to bedroom
of hotels, motels, resorts, private hospital
rooms and the like
May include bath, shower and
water closet in one compartment.
Rate is independent of room size
(see Note 2)
Higher air quantities may be
required for vapour control or
removal
(Handbasins are not considered
as a ‘listed fixture’)
Operation of the system may be
intermittent
Sewage ejection
100
L/s
Minimum
(continued)
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AS 1668.2—2012
70
TABLE B1 (continued)
Enclosure type
Quantity
Unit
Comments
Spas and hydrotherapy pools
15
L/s.m2
Pool and deck areas
10
L/s.m2
For areas operating above 30°C,
or with agitated water surfaces,
higher ventilation rates may be
applicable
Swimming pools
A2
For the purposes of determining
pool area, this is equal to 115%
pool surface area (to
accommodate splash area)
Higher values may also be
required for humidity control
Plant room/storage room
5
L/s.m2 floor
Enclosures used for storage of
equipment, plant or materials
likely to contaminate the air will
need special consideration (see
Appendix O).
Lifts
Lift car and motor room
ventilation, see AS 1735.1
Refrigeration
See AS/NZS 1677.2
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NOTES:
1
Enclosure uses in Table B1 are typical. Omission of an applicable enclosure from this Table does not
obviate the need to comply, in principle, with this Standard (see Section 3).
2
Where a bathroom is combined with a laundry, the higher of the two applicable ventilation rates may be
used.
3
Unit ‘L/s.m2 floor’ shall be read as ‘L/s per square metre of floor area’.
4
For the purposes of minimizing contaminant levels, exhaust from swimming pool enclosures shall include
low level intakes, positioned as close as practicable to the pool surface area.
5
Pool areas shall be kept at a negative pressure relative to adjacent non-associated enclosures (associated
enclosures may include pool change rooms, spa areas and spectator areas).
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AS 1668.2—2012
APPENDIX C
OUTDOOR AIR CONTAMINANT LEVELS
(Informative)
Values for maximum acceptable concentrations of some contaminants in outdoor air
adopted by the National Environment Protection Council (NEPC) are provided in Table C1.
TABLE C1
RECOMMENDED MAXIMUM ACCEPTABLE CONCENTRATIONS
OF SOME CONTAMINANTS IN OUTDOOR AIR
Contaminant
Exposure limit
Condition
Carbon monoxide (CO)
8h
9.0 ppm
1 day a year
Nitrogen dioxide (NO 2 )
1h
0.12 ppm
1 day a year
1 year
0.03 ppm
None
1h
0.10 ppm
1 day a year
4h
0.08 ppm
1 day a year
1h
0.20 ppm
1 day a year
1 day
0.08 ppm
1 day a year
1 year
0.02 ppm
None
1 year
0.50 g/m3
None
Photochemical oxidants
(as ozone)
Sulfur dioxide (SO 2 )
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Exposure time
Lead (Pb)
Particles as PM10
1 day
50.0
g/m3
5 days a year
LEGEND:
ppm = parts per million by volume
g/m3 = micrograms per cubic metre
NOTE: Refer to the NEPC for updates on the recommended maximum acceptable
concentrations for these and other contaminants in outdoor air.
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 Standards Australia
AS 1668.2—2012
72
APPENDIX D
PRINCIPLES OF VENTILATION AIRFLOW ANALYSIS
(Normative)
D1 GENERAL
The requirements of this Standard are met by providing the minimum effective outdoor air
required by Appendix A for each enclosure(s) served by the ventilation system while not
reducing the minimum concentration of introduced outdoor air below 7.5 L/s.person where
particulate filtration is provided or 2.5 L/s.person where odour filtration is provided. This
may be achieved by bringing in outdoor air directly into the system (introduced outdoor
air), by using residual outdoor air in recycle or transfer airstreams, by using air-cleaning
devices to provide an equivalent outdoor air effect, or by a combination of these.
The combination of all these outdoor air types or strategies is called ‘effective outdoor’ air.
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Effective outdoor air (q eff) may be provided in a number of ways, as follows:
(a)
Introducing outdoor air directly into the system from outdoors (i.e. introduced
outdoor air).
(b)
Utilizing unused outdoor air in a local system (i.e. residual recycle outdoor air).
(c)
Utilizing unused outdoor air in transfer or make-up airstream (i.e. residual transferred
outdoor air).
(d)
Cleaning recirculated air to provide an equivalent dilution effect (i.e. equivalent
outdoor air).
All enclosures served by an air-handling system shall be deemed to be ventilated at the
required rate if, for each enclosure, the following is satisfied and the system introduced
outdoor airflow rate (Qf) is not less than that determined in accordance with Paragraph D3:
q eff  q min
and the system introduced outdoor airflow rate (Qf) is not less than that determined in
accordance with Paragraph D3.
Where q eff = the sum of all effective outdoor air delivered to the enclosure, including the
effective outdoor air in the supply air, effective outdoor air from local air cleaning and the
proportion of effective outdoor air within transfer air.
With no supply air cleaning:
q eff = q eff(s) + q eff(l) + q res(t)
With supply air and recycle air cleaning:
q eff = q eff(sʹ) + q eff(l) + q res(t)
Where local air cleaning is provided, calculations for enclosures without local air cleaning
shall be made for the system in the absence of local air cleaning, but the value of rc used to
determine Q f shall be based on the highest ratio of q min/q s for enclosures without local air
cleaning. Then the airflow rate and efficiency of the local air-cleaning unit(s) shall be as
necessary to ensure that, for each enclosure, the effective outdoor air supplied via the
supply air system and the local air-cleaning unit is not less than q min.
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AS 1668.2—2012
D2 NOTATION
The following symbols are used in this Appendix.
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A2
A2
ec
= the fractional efficiency (percentage efficiency divided by 100) of the central
air-cleaning unit for the contaminant under all operating conditions, determined
in accordance with Paragraph D5
el
= the fractional efficiency (percentage efficiency divided by 100) of a local
air-cleaning unit, if provided, for the contaminant under all operating conditions,
determined in accordance with Paragraph D5
es
= the fractional efficiency (percentage efficiency divided by 100) of a supply
air-cleaning unit, if provided, for the contaminant under all operating conditions,
determined in accordance with Paragraph D5
M
= multiple enclosure factor
Qeff
= the actual volume of effective outdoor air in the system supply air, in litres per
second
Qf
= the flow rate of introduced outdoor air to the system, in litres per second
Qr
= the flow rate of return air drawn from all enclosures served by an air-handling
system to be used as recycle air, in litres per second
Qs
= the flow rate of supply air to all enclosures served by an air-handling system, in
litres per second
Qres
= the sum of the residual effective outdoor airflow rate from all enclosures served,
in litres per second
qf
= outdoor air per person required to be introduced into an enclosure in accordance
with Table A1
ql
= the rate at which air is recycled through a local air-cleaning unit, in litres per
second
qr
= the flow rate at which return air to be used as recycle air is drawn from an
enclosure, in litres per second
qs
= the flow rate of supply air to the enclosure, in litres per second
qt
= the flow rate of transfer air to the enclosure, in litres per second
q res
= the actual volume of residual effective outdoor air in the enclosure, in litres per
second
q eff
= the actual volume of effective outdoor air supplied to the enclosure, in litres per
second
qmin
= the required minimum effective outdoor air to be supplied to the enclosure, in
litres per second
qres(t)
= the flow rate of residual outdoor air in transfer air to the enclosure, in litres per
second
q eff(s)
= the flow rate of effective outdoor air in supply air to the enclosure prior to any
supply air cleaning, in litres per second
qeff(s ) = the flow rate of effective outdoor air in supply air to the enclosure after any
supply air cleaning, in litres per second
q eff(l)
= the flow rate of effective outdoor air provided by local air cleaning, in litres per
second
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 Standards Australia
AS 1668.2—2012
74
R
= the ratio of the sum of required effective outdoor airflow rates for all enclosures
served to the total supply air for all enclosures served
r
= the ratio of supply air to required introduced outdoor air for each enclosure
rc
= the highest ratio, for any of the enclosures served, of effective outdoor airflow
required by Clause 2.8.3 to the corresponding supply air
rc
= the highest ratio of q min/q s for all enclosures served where local air cleaning,
supply air cleaning or transfer air is not proposed
n
= the occupancy for the enclosure served, as defined in Clause 2.2.2
D3 MINIMUM INTRODUCED OUTDOOR AIRFLOW RATE
When a system is in a state of equilibrium, an enclosure that is ventilated with introduced
outdoor airflow at exactly the required minimum rate for its occupancy and area will be
contaminated at the allowable limit, so recycle air drawn from the enclosure has no residual
introduced outdoor airflow.
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When an enclosure is ventilated with introduced outdoor airflow at more than the minimum
required rate, its air is not fully contaminated, so recycle air drawn from it has residual
introduced outdoor airflow. This residual introduced outdoor air may be recycled back into
the supply air system, which will effectively reduce the total amount of introduced outdoor
air necessary to satisfy the requirements of the enclosure with the highest proportional
demand.
The use of air-cleaning devices shall not permit introduced outdoor airflow rates to be
reduced below the greater of the area based minimum and the occupancy-based minimum,
as follows:
Area based minimum:
Qf = A  0.35 L/s.m2
Occupancy based minimum:
Qf = n  7.5 L/s
(where only particulate filtration in accordance with Appendix D is proposed for a
single enclosure system); or
Qf = n  7.5 L/s  M
(where only particulate filtration in accordance with Appendix D is proposed for a
multiple enclosure system); or
Qf = n  2.5 L/s
(where particulate filtration and odour treatment in accordance with Appendix D are
proposed for a single enclosure system); or
Qf = n  2.5 L/s  M
(where particulate filtration and odour treatment in accordance with Appendix D are
proposed for a multiple enclosure system)
The ratio (r) of supply air (q s) to required introduced outdoor air (q f) for each enclosure
may be calculated as follows:
r = q f /q s
. . . D3(1)
The highest ratio of r is determined to be rc.
The ratio (R) of the sum of minimum introduced outdoor air (q f) to the total supply air
(Qs) may be calculated as follows:
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 Standards Australia
75
R = (q f)/Qs
AS 1668.2—2012
. . . D3(2)
The multiple enclosure factor (M) may be calculated as follows:
M = 1/(1 + R  rc)
. . . D3(3)
NOTE: The derivation of M is based on an assumption that q r /qs is similar for all enclosures.
The system’s minimum introduced outdoor airflow rate (Qf) may then be calculated as
follows:
Qf = M  (q f)
. . . D3(4)
Where two or more adjoining enclosures are proposed to utilize transfer air and the transfer
air reasonably sweeps through the entire enclosure receiving the transfer air, then for the
purposes of the above calculation the adjoining enclosures may be considered as a single
enclosure.
Once the minimum introduced outdoor airflow rate has been determined, the additional
requirements for air cleaning, transfer air and residual effective outdoor air necessary to
achieve the minimum effective outdoor airflow can be determined.
D4 RESIDUAL EFFECTIVE OUTDOOR AIRFLOW
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D4.1 General
When a system is in a state of equilibrium, an enclosure that is ventilated with effective
outdoor airflow at exactly the required minimum rate for its occupancy will be
contaminated at the allowable limit, so recycle air drawn from the enclosure has no residual
effective outdoor airflow. When an enclosure is ventilated with effective outdoor airflow at
more than the minimum required rate, its air is not fully contaminated, so recycle air drawn
from it has residual effective outdoor airflow (qres). The residual effective outdoor airflow
(qres) may be determined from the following equation:
q res = q eff  qmin
. . . D4.1
Where local air cleaning is used to achieve the required effective outdoor airflow in an
enclosure, the calculated residual effective outside air shall be based on the assumption that
no local air cleaning occurs, to ensure that the air quality for occupants in other enclosures
meets the requirements if the local air-cleaning unit is not working.
D4.2 Effective outdoor airflow from recycle air
To analyse the effective outdoor airflow achieved by a ventilation system if measures such
as the use of recycle air with residual effective outdoor airflow to increase the amount of
effective outdoor airflow supplied to enclosures or, if factors such as variable supply
airflow may decrease the amount of effective outdoor airflow supplied to enclosures, it is
necessary to determine the extent to which recycle air has unused or residual effective
outdoor airflow.
The extent to which residual effective outdoor air can be recycled or transferred to other
enclosures will depend upon the ratio of supply air:recycle air and the extent of local and
general exhaust in the enclosure or adjacent enclosures.
The residual effective outdoor air (q res) entering the recycle air may be determined from the
following equation:
q res = (q eff  q min)  q r /q s
. . . D4.2
Where local air cleaning is used to achieve the required effective outdoor airflow in an
enclosure, no residual effective outside air shall be used from that enclosure in the
summation calculation for the amount of effective outdoor air in the recycle air (q res = 0 for
that enclosure), to ensure that the air quality for occupants in other enclosures meets the
requirements if the local air cleaning unit is not working.
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 Standards Australia
AS 1668.2—2012
76
D4.3 Effective outdoor airflow from transfer air
Where use is made of transfer air (q t) from another enclosure with residual effective
outdoor air (q res), for the enclosure served, q eff is increased by an amount where—
A2
q res(t) = qt  qres/qs
. . . D4.3
Where q res and qs refer to the values of the enclosure from where the transfer air is drawn.
Transfer air may only be used to provide effective outdoor air to another enclosure where
the transfer air reasonably sweeps through the entire enclosure that it is providing effective
outdoor air to prior to entering the recycle air system.
D4.4 Effective outdoor airflow from local air cleaning
Where a system incorporates local air-cleaning devices, it is possible to increase the
effective outdoor airflow of local air by treating it to remove contaminants. To use local air
cleaning for this purpose, air-cleaning devices shall be effective at removing contaminants
associated with occupancy, such as particulates and odours.
If treatment of local air is used to remove contaminants, the effective outdoor airflow
increases by an amount that depends on the efficiency of the local air treatment. The
fractional efficiency of the local air treatment system (el) used in calculations shall be in
accordance with Paragraph D6.
Where local air treatment is provided, the effective outdoor airflow shall satisfy the
following:
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A2
qeff(1) 
q1  e1
1.5
. . . D4.4
NOTE: The factor of 1.5 is a conservative multiplier used to account for non-uniform air cleaning
effectiveness across the enclosure.
Local air cleaners shall be reasonably evenly distributed throughout the enclosure.
No credit is permissible in the calculation for the increase in the effective outdoor air in the
recycle or transfer air arising from the use of the local air-cleaning unit, to ensure that the
air quality for occupants in other enclosures meets the requirements if the local air-cleaning
unit is not working.
D4.5 Effective outdoor airflow from supply air cleaning
Where a system incorporates supply air-cleaning devices, it is possible to increase the
effective outdoor airflow of supply air by treating it to remove contaminants. To use supply
air cleaning for this purpose, air-cleaning devices shall be effective at removing
contaminants such as particulates and odours associated with occupancy.
A2
If treatment of supply air is used to remove contaminants, the effective outdoor airflow
increases by an amount that depends on the efficiency of the supply air treatment. The
fractional efficiency of the supply air treatment (es) used in calculations shall be in
accordance with Paragraph D5.
Where supply air treatment is provided, the effective outdoor airflow shall satisfy the
following:
A2
q eff(s ) = (qs  q eff(s))  es + q eff(s)
. . . D4.5
NOTE: The use of supply air cleaning may lead to a requirement for iterative calculation.
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 Standards Australia
77
AS 1668.2—2012
D4.6 Effective outdoor airflow from central air cleaning
Where a system incorporates central air-cleaning devices, the effective outdoor airflow of
the recycle air may be increased by treating it to remove contaminants. To use recycle air
treatment for this purpose, air-cleaning devices shall be effective at removing contaminants
such as particulates and odours associated with occupancy. Only the portion of the recycle
air that is not already considered to be residual effective outside air may be considered to be
improved through central air cleaning.
If central cleaning of recycle air is used to remove contaminants, the effective outdoor
airflow increases by an amount that depends on the efficiency of the recycle air treatment.
The fractional efficiency of the recycle air treatment (ec) used in calculations shall be in
accordance with Paragraph D5.
Where central recycle air treatment is provided, the effective outdoor airflow rate in the
supply air to each enclosure may then be calculated as follows:
A1
A2
‘Text deleted’
qeff(s) = qs  [(Qs  Qres  Qf)  ec + Qf ]/Qs
. . . D4.6
D5 EFFICIENCIES OF AIR-CLEANING UNITS
D5.1 General
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The efficiency of air-cleaning units shall be determined using a test method that accurately
assesses the performance of the air-cleaning unit for the contaminant concerned.
D5.2 Test methods for odours
The efficiency of the air-cleaning unit for removal of odours shall be determined by a
suitable test.
D5.3 Test methods for particulate contaminants
The efficiency of the air-cleaning unit for removal of particulates shall be as given in
Table D1, determined in accordance with AS 1324.2 using Test Dust No. 1 and average
efficiencies.
Where filtration of a specific efficiency has been applied in accordance with this Standard
to reduce the minimum outdoor air requirements, provisions shall be made to facilitate
convenient routine maintenance or replacement of filters with the same efficiency.
TABLE D1
FILTER PARTICULATE EFFICIENCIES—BY CLASS
A2
www.standards.org.au
Class
Percentage average
efficiency
(E m)
Fractional efficiency for the
purpose of calculations
Undefined
20 < E m < 40
Not applicable
F5
40 < E m < 60
0.40
F6
60 < E m < 80
0.60
F7
80 < E m < 90
0.80
F8
90 < E m < 95
0.90
F9
95 < E m
0.95
 Standards Australia
AS 1668.2—2012
78
D6 CALCULATION PROCEDURE
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A2
The following is a suggested sequence for calculations:
Step 1
Calculate the required minimum effective outdoor airflow (q min) for each
enclosure served through reference to Table A1 in Appendix A (q f).
Step 2
Calculate the ratio of required effective outdoor airflow to supply air (r) for all
enclosures where supply air cleaning, local air cleaning and transfer air are not
proposed.
Step 3
Determine the highest ratio of r = rc
Step 4
Calculate the minimum required effective outside air for the supply air
Qeff = rc  Qs.
Step 5
Calculate the ratio (R) of the sum of minimum introduced outdoor air (q r) to the
total supply air Qs.
Step 6
Calculate the multiple enclosure factor (M)  (Provided that q r/qs is reasonably
similar for all enclosures)
Step 7
Calculate the system’s minimum introduced outdoor air rate (Qf) ensuring that
rates are not reduced below 7.5 L/s.person when air-cleaning devices for
particulate only are used and 2.5 L/s.person when air-cleaning devices for
particulate and odour are used.
Step 8
Calculate the residual effective outdoor air from each enclosure that will be
recycled.
Step 9
Calculate the central air cleaner efficiency required to achieve Qeff as calculated
in Step 4.
Step 10
Where proposed, calculate required supply air-cleaning device efficiency,
recirculation air cleaner efficiency and/or volume flow rate, volume of transfer
air required to meet or exceed the required effective outdoor airflow rate for each
enclosure by assuming that the quantity of effective outdoor air in the supply air
will be equal to rmax  q s (iterative procedures may be required).
Step 11
Check that the introduced outdoor airflow rate is greater than the sum of any
exhaust airflow rates.
D7 EXAMPLE (Central air cleaning—Particulate filtration only)
A constant volume system serving a typical office arrangement with four enclosures.
Enclosure 1—Office accommodation for 16 people with a supply air quantity of
1000 L/s.
Enclosure 2—Office accommodation for 38 people with a supply air quantity of
2500 L/s.
Enclosure 3—A meeting room for 20 people with a supply air quantity of 450 L/s.
Enclosure 4—A board room for 10 people with a supply air quantity of 250 L/s.
Step 1—Assuming particulate
air = 7.5 L/s.person)
filtration
only
(minimum
introduced
outside
Calculate the required minimum effective outdoor airflow (qmin) for each enclosure
served through reference to Table A1 in Appendix A (q f).
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79
AS 1668.2—2012
A2
Enclosure
n
(People)
qs
(L/s)
qf
(from Table A1)
q min
(q f  n)
1
16
1000
10
160
2
38
2500
10
380
3
20
450
10
200
4
10
250
10
100
Step 2—
Calculate the ratio of required effective outdoor airflow to supply air (r) for all
enclosures where supply air cleaning, local air cleaning and transfer air are not
proposed.
Enclosure
n
(People)
qs
(L/s)
qf
(from Table A1)
q min
(q f  n)
r
(q min/q s)
1
16
1000
10
160
0.16
2
38
2500
10
380
0.152
3
20
450
10
200
0.444
4
10
250
10
100
0.4
Step 3—
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Determine the highest ratio of r = rc
Enclosure
n
(People)
qs
(L/s)
qf
(from Table A1)
q min
(q f  n)
r
(qmin/q s)
1
16
1000
10
160
0.16
2
38
2500
10
380
0.152
3
20
450
10
200
0.444
4
10
250
10
100
0.4
rc = 0.444
Step 4—
Calculate the minimum required effective outdoor air for the supply air
Qeff = rc  Qs.
n
Enclosure (People)
qs
(L/s)
qf
(from Table A1)
q min
(q f  n)
r
(q min/q s)
1
16
1000
10
160
0.16
2
38
2500
10
380
0.152
3
20
450
10
200
0.444
4
10
250
10
100
0.4
N = 84
Qs =4200
(q min) = 840
rc = 0.444
Qeff = rc  Qs
Qeff = 0.444  4200
Qeff = 1865 L/s
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 Standards Australia
AS 1668.2—2012
A2
80
Step 5—
The ratio (R) of the sum of minimum introduced outdoor air (q r) to the total supply
air (Qs) may be calculated as follows:
R = N  7.5/Qs
R = 630/4200
R = 0.15
Step 6—
The multiple enclosure factor (M) may be calculated as follows:
M = 1/(1 + R  rc )
M = 1/(1 + 0.15  0.444)
M = 1.42
Step 7—
The system’s minimum introduced outdoor airflow rate (Qf) may then be calculated
as follows:
Qf = M  N  7.5
Qf = 1.42  630
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Qf = 895 L/s (approximately 10.7 L/s.person)
Step 8—
Calculate the residual effective outdoor air from each enclosure that will be recycled.
qres = (q eff  q min)  q r/q s
For the purposes of this example it is assumed that the amount of recycle air drawn
from each enclosure q r is proportional to the ratio of introduced outside air to supply
air (1  895/4200 = 0.79). Therefore for this example q r/qs = 0.79.
Therefore, for Enclosure 1—
q eff = qs  rc
q eff = 1000  0.444
q eff = 444 L/s
q res = (444  160)  0.79
qres = 224 L/s
Repeat for each enclosure.
n
(People)
qs
(L/s)
qf
(from
Table A1)
q min
(q f  n)
(q min/q s)
1
16
1000
10
160
0.16
224
2
38
2500
10
380
0.152
577
3
20
450
10
200
0.444
0
4
10
250
10
100
0.4
9
N = 84
Qs =4200
Enclosure
www.standards.org.au
r
(q min) = 840 rc = 0.444
( q eff
q res
 q min)  q r/qs
(L/s)
(qres) = 810
 Standards Australia
81
A2
AS 1668.2—2012
Step 9—
Calculate the central air cleaner efficiency required to achieve Qeff as calculated in
Step 4.
ec = [Qeff  Qf  (qres)]/[Qs  Qf  (qres)]
ec 
1865  895  810 
4200  895  810 
ec = 0.064(6.5%)
Based on Table D1, a filter of nominal 20% efficiency would more than satisfy this
6.5% efficiency requirement.
Step 10—(is not required in this instance)
Step 11—(exhaust is not included in this example)
D8 EXAMPLE (Central air cleaning—Particulate filtration and odour treatment)
A constant volume system serving a typical office arrangement with four enclosures.
Enclosure 1—Office accommodation for 16 people with a supply air quantity of 1000 L/s.
Enclosure 2—Office accommodation for 38 people with a supply air quantity of 2500 L/s.
Enclosure 3—A meeting room for 20 people with a supply air quantity of 450 L/s.
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Enclosure 4—A board room for 10 people with a supply air quantity of 250 L/s.
Step 1—Assuming particulate filtration and odour treatment (minimum introduced outside
air = 2.5 L/s.person)
Calculate the required minimum effective outdoor airflow (q min) for each enclosure served
through reference to Table A1 in Appendix A (q f).
Enclosure
n
(People)
qs
(L/s)
qf
(from Table A1)
q min
(q f  n)
1
16
1000
10
160
2
38
2500
10
380
3
20
450
10
200
4
10
250
10
100
Step 2—
Calculate the ratio of required effective outdoor airflow to supply air (r) for all enclosures
where supply air cleaning, local air cleaning and transfer air are not proposed.
Enclosure
n
(People)
qs
(L/s)
qf
(from Table A1)
q min
(q f  n)
r
(q min/q s)
1
16
1000
10
160
0.16
2
38
2500
10
380
0.152
3
20
450
10
200
0.444
4
10
250
10
100
0.4
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 Standards Australia
AS 1668.2—2012
A2
82
Step 3—
Determine the highest ratio of r = rc .
Enclosure
n
(People)
qs
(L/s)
qf
(from Table A1)
q min
(q f  n)
r
(q min/q s)
1
16
1000
10
160
0.16
2
38
2500
10
380
0.152
3
20
450
10
200
0.444
4
10
250
10
100
0.4
rc = 0.444
Step 4—
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Calculate the minimum required effective outdoor air for the supply air Qeff = rc  Qs.
Enclosure
n
(People)
qs
(L/s)
qf
(from Table A1)
q min
(q f  n)
r
(q min/q s)
1
16
1000
10
160
0.16
2
38
2500
10
380
0.152
3
20
450
10
200
0.444
4
10
250
10
100
0.4
N = 84
Qs =4200
(q min) = 840
rc = 0.444
Qeff = rc  Qs
Qeff = 0.444  4200
Qeff = 1865 L/s
Step 5—
The ratio (R) of the sum of minimum introduced outdoor air (q r) to the total supply air
(Qs) may be calculated as follows:
R = N  2.5/Qs
R = 210/4200
R = 0.05
Step 6—
The multiple enclosure factor (M) may be calculated as follows:
M = 1/(1 + R  rc )
M = 1/(1 + 0.05  0.444)
M = 1.65
Step 7—
The system’s minimum introduced outdoor airflow rate (Qf) may then be calculated as
follows:
Qf = M  N  2.5
Qf = 1.65  210
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 Standards Australia
83
A2
AS 1668.2—2012
Qf = 347 L/s (approximately 4.1 L/s.person)
Step 8—
Calculate the residual effective outdoor air from each enclosure that will be recycled.
q res = (q eff  q min)  q r/q s
For the purposes of this example it is assumed that the amount of recycle air drawn from
each enclosure q r is proportional to the ratio of introduced outside air to supply air.
(1  347/4200 = 0.92) Therefore for this example qr/q s = 0.92.
Therefore, for Enclosure 1—
q eff = qs  rc
q eff = 1000  0.444
q eff = 444 L/s
q res = (444  160)  0.92
qres = 224 L/s
Repeat for each enclosure.
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n
Enclosure (People)
qs
(L/s)
qf
(from
Table A1)
qmin
(q f  n)
(q min/q s)
r
( q eff
q res
 q min)  q r/qs
(L/s)
1
16
1000
10
160
0.16
261
2
38
2500
10
380
0.152
672
3
20
450
10
200
0.444
0
4
10
250
10
100
0.4
10
N = 84
Qs =4200
(q min) = 840 rc = 0.444
(q res) = 943
Step 9—
Calculate the central air cleaner efficiency required to achieve Qeff as calculated in Step 4.
ec = [Qeff  Qf  (qres)]/[Qs  Qf  (qres)]
ec 
1865  347  943
4200  347  943
ec = 0.20(20%)
A filter or air-treatment system with a tested efficiency of 20% for body odour reduction
would satisfy this requirement when combined with a particulate filter that also achieves a
20% particulate efficiency requirement.
Based on Table D1, an F5 filter of nominal 20% efficiency would satisfy this 20%
particulate efficiency requirement (however it would not achieve the required odour
reduction without odour treatment).
Step 10—(is not required in this instance).
Step 11—(exhaust is not included in this example)
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 Standards Australia
AS 1668.2—2012
84
APPENDIX E
KITCHEN EXHAUST HOODS
(Normative)
E1 SCOPE
This Appendix sets out requirements for the construction and installation of kitchen exhaust
hoods where their provision is required under Clause 3.4.
E2 APPLICATION
Where a kitchen exhaust hood is required, it shall comply with Paragraphs E3, E4 and E9,
and, where grease vapour is present, it shall also comply with Paragraphs E5 or E6 and
Paragraph E7.
E3 HOOD CONSTRUCTION
E3.1 General
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Hoods shall be designed—
(a)
to capture cooking vapours and associated products of combustion;
(b)
to exhaust cooking vapours and associated products of combustion together with
dilution air;
(c)
to prevent condensate falling onto the food, cooking appliance(s) or the floor;
(d)
to permit easy access to cleaning spaces where condensate may accumulate;
(e)
with vertical flat sides where walls abut; and
(f)
to be free of insulation material on the internal surface of the hood or exhaust plenum
between the hood and connecting duct.
E3.2 Manufacture
A2
Hoods shall be manufactured from rigid impervious hard-faced material deemed
non-combustible when tested in accordance with AS 1530.1, such as steel or stainless steel,
reinforced where necessary to provide stability and rigidity with smooth-faced liquid-tight
seams and joints made by appropriate methods, such as the following:
(a)
Continuous welding.
(b)
Grooving or lapping, riveting and continuous soldering.
(c)
Continuous jointing and sealing with an appropriate compound unaffected by grease,
water or cleaning agents that are in compression at the joint.
E3.3 Openings
Exhaust openings in hoods shall be—
(a)
suitably located in relation to the types of cooking and heating appliances being
ventilated and positioned so that a uniform hood velocity is maintained;
(b)
not more than 500 mm from the extremities of the exhaust plenum, not more than 1 m
apart, and of dimensions that permit access into the exhaust plenum for cleaning
purposes; and
NOTE: For exhaust openings in hoods, see Figure E3.
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designed to prevent condensate from the top surface of the exhaust plenum or duct
from falling through the exhaust opening.
NOTE: Removable panels between filters provide easy access to exhaust plenum for cleaning.
E3.4 Internal surface
E3.4.1 Sloping
All surfaces of hoods exposed to the appliance being ventilated shall be sloped at an angle
not greater than 40° from the vertical (see also Paragraph E5), unless the design and
performance of hoods prevent the formation of any condensate on such surfaces.
E3.4.2 Profile
The surfaces of the canopy hood that are exposed to the appliance being ventilated shall be
free of stiffeners or any protrusions, other than fire extinguisher heads, which shall be
installed in accordance with AS 3772.
E3.4.3 Hood gutters
Hood gutters not less than 50 mm wide and not less than 25 mm deep shall be provided
around the lower edges of canopy type hoods and shall include 25 mm min diameter
drainage holes fitted with removable caps.
For low sidewall hoods, grease may be drained into removable collection containers.
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E3.4.4 Distance from grease gutter to perimeter of appliance
In a canopy type kitchen exhaust hood, the inside edge of the grease gutter shall be not less
than 150 mm beyond the plan perimeter of the appliance over which the hood is installed
for cooking processes Types 1 to 4 and 300 mm for cooking process Type 5, except on sides
adjoining a wall.
E3.4.5 Internal light fittings
Where fitted, internal light fittings shall be flush-mounted.
NOTE: Access from the outside face of the hood avoids disturbing the vapour seal to the inside
face of the hood during servicing.
E4 HOOD INSTALLATION
The lower edge of a canopy type kitchen exhaust hood shall be not less than 2 m above
floor level at the operator side of the appliance being ventilated and no higher than 1.2 m
above the cooking appliance.
E5 KITCHEN
FILTERS
EXHAUST
HOODS
INCORPORATING
GREASE-REMOVAL
Hoods shall incorporate a device that will impede the process of grease within the airstream
in accordance with the following:
A2
(a)
Filter media and holding frame shall be constructed of rigid material and deemed
non-combustible when tested in accordance with AS 1530.1.
(b)
The number, size and distribution of the filters shall be such that the air temperature
and flow rate through each filter is within the manufacturer’s design limits.
(c)
Filters shall be installed so as to prevent significant leakage of air around their
perimeter.
(d)
The faces of filters shall be either vertical or sloped at an angle not greater than 30°
from vertical.
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86
The filters shall be fitted at exhaust openings of the hood so that any grease draining
from filters is collected and disposed of without spilling or otherwise contaminating
the kitchen area.
NOTE: An example would be a filter support channel designed to collect and convey grease
into hood gutter.
(f)
The filters and the filter-retaining devices shall be flush-mounted to comply with
Paragraph E3.4.2.
(g)
The filters shall be removable by hand, without the need of tools, for the purposes of
their cleaning and the cleaning of the supports and the grease drainage devices, unless
an in situ washing system is provided.
E6 KITCHEN
DEVICES
EXHAUST
HOODS
INCORPORATING
GREASE-REMOVAL
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Kitchen exhaust hoods incorporating grease-removal devices other than those in
Paragraph E5 shall—
(a)
remove grease from the cooking vapours;
(b)
prevent grease from falling back onto food, the cooking appliance or floor;
(c)
provide for manual or automatic cleaning of grease-removal devices, and all internal
surfaces of the device housing; and
(d)
be demonstrated to capture and remove cooking vapours and grease with efficiency at
least equal to that of kitchen exhaust hoods complying with Paragraph E5.
E7 DISTANCE FROM GREASE-REMOVAL DEVICE TO HEAT SOURCE
E7.1 General
A2
A2
Unless otherwise reduced, the distance between the lowest edge of a grease-removal device
and the cooking surface shall be not less than—
(a)
1350 mm—for charcoal and similar type of open fires, including where food is
typically ignited during the cooking process;
(b)
1050 mm—where the heat source is provided by means of a naked flame (e.g. gas
stove);
(c)
600 mm—where the heat source is provided by electrically operated equipment or a
fixed plate or pan above gas flame (e.g. solid grill plate or deep fryer); and
(d)
200 mm—for kebab cooker and salamander.
E7.2 Text deleted
E8 KITCHEN EXHAUST HOOD AIRFLOW—CALCULATIONS—EXAMPLES
E8.1 General
This Paragraph includes examples of airflow calculations for typical installation and
diagrams of different types of kitchen exhaust canopy hoods detailing the required
overhang.
E8.2 Low sidewall hoods (hood Type 1) calculation example
A2
For this example, Type 4 process is the highest grease-producing cooking.
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Using the formula from Table 3.1 and Figure E1:
Q = 800  L
where
L = inside length of hood = 3600 mm
then
Q = 800  3.6 = 2880 L/s
3.6
0.15
0.9
0.9
A
B
0.6
C
0.9
C
0.15
D
0.9
0.15
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Kitchen equipment
Cooking process type
A Range
Type 3
B Gas barbecue
Type 4
C Electric deep fryer
Type 3
D Steam kettle
Type 2
DIMENSIONS IN METRES
FIGURE E1 PLAN OF KITCHEN EQUIPMENT AGAINST WALL
E8.3 Corner-mounted hoods (hood Type 2) calculation example
(Assume that the distance from the bottom of the hood to the top of the cooking equipment
is 1.2 m).
For this example, Type 4 is the highest grease-producing cooking process. Therefore, the
required overhang is 150 mm.
Using the formula from Table 3.1:
Q = 375  P  H
where
P = W + L = 1050 mm + 3600 mm = 4650 mm
then
Q = 375  4.65  1.2 = 2092.5 L/s
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E8.4 Sidewall hoods (hood Type 3) calculation example
(Assume that the distance from the bottom of the hood to the top of the cooking equipment
is 1.2 m.)
For this example, Type 4 is the highest grease-producing cooking process. Therefore, the
required overhang is 150 mm.
Using the formula from Table 3.1 and Figure E2:
Q = 375  P  H
where
P = 2W + L = (2  1050 mm) + 3600 mm = 5700 mm
then
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Q = 375  5.7  1.2 = 2565 L/s
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3.9
0.15
0.9
0.9
0.9
0.9
C
D
0.15
0.15
0.9
A
0.9
E
B
B
B
2.4
F
G
G
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0.4 5
Kitchen equipment
Cooking process type
A Range
Type 3
B Electric deep fryers
Type 3
C Hot top range
Type 3
D Gas BBQ
Type 4
E Blast freezer
Type 1
F Gas oven
Type 2
G Steam kettle
Type 2
DIMENSIONS IN METRES
FIGURE E2 PLAN OF KITCHEN EQUIPMENT UNDER ISLAND HOOD
E8.5 Island hoods (hood Type 4) calculation example
(Assume that the distance from the bottom of the hood to the top of the cooking equipment
is 1.2 m.)
For this example, Type 4 is the highest grease-producing cooking process. Therefore, the
required overhang is 150 mm on one side of the hood and due to the gas-fired oven the
overhang is 450 mm on the other side.
Using the formula from Table 3.1:
Q = 375  P  H
where
P = 2W + 2L = (2  2400 mm) + (2  3900 mm) = 12 600 mm
then
Q = 375  12.6  1.2 = 5670 L/s
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E9 HOOD TYPE NOMENCLATURE
Indicative sketches for common hood types are given in Figures E3, E4, E5, E6, E7, E8, E9,
E10 and E11.
500 mm
m a x.
A
10 0 0 m m
G r e a s e - r e m ova l
f il te r s
Exhaust plenum
3 0 ° m a x.
H o o d g u t te r
Side skirt
Side skirt
See
C l a u s e 17.1
C o o k i n g a p p li a n c e
A
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FR O N T V I E W
S ECT I O N A - A
FIGURE E3 TYPICAL LOW SIDEWALL (BACK SHELF) TYPE 1 HOOD
INCORPORATING GREASE-REMOVAL FILTERS
Exhaust duct
10 0 0 m a x.
50 0 ma x.
Exhaust plenum
G r e a s e - r e m ova l
f il te r s
A
40° max.
3 0 ° m a x.
H o o d g u t te r
W
120 0 m a x. h e i g ht
ove r c o o k i n g a p p li a n c e (H )
150 m i n.
See
C l a u s e I7.1
20 0 0 m i n.
C o o k i n g a p p li a n c e
A
L
150 m i n.
ove r h a n g at
a ll f r e e s i d e s
FR O N T V I E W
S ECT I O N A - A
DIMENSIONS IN MILLIMETRES
FIGURE E4 TYPICAL CORNER-MOUNTED HOOD TYPE 2—INCORPORATING
GREASE-REMOVAL DEVICES
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AS 1668.2—2012
Exhaust duct
10 0 0 m a x.
50 0 ma x.
Exhaust plenum
G r e a s e - r e m ova l
f il te r s
A
40° max.
3 0 ° m a x.
H o o d g u t te r
W
120 0 m a x. h e i g ht
(H )
ove r c o o k i n g a p p li a n c e (H
See
C l a u s e I7.1
150 m i n.
20 0 0 m i n.
C o o k i n g a p p li a n c e
150 m i n.
ove r h a n g a t
a ll f r e e s i d e s
A
150 m i n.
L
FR O N T V I E W
S ECT I O N A - A
DIMENSIONS IN MILLIMETRES
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FIGURE E5 TYPICAL TYPE 3 SIDEWALL HOOD CANOPY
INCORPORATING GREASE-REMOVAL DEVICES
Exhaust duct
10 0 0 m a x.
50 0 ma x.
A
Exhaust duct
G r e a s e - r e m ova l
f il te r s
Exhaust plenum
40° max.
3 0 ° m a x.
H o o d g u t te r
W
120 0 m a x. h e i g ht
ove r c o o k i n g a p p li a n c e (H )
150 m i n.
See
C l a u s e I7.1
20 0 0 m i n.
C o o k i n g a p p li a n c e
A
150 m i n.
L
150 m i n.
ove r h a n g
all round
FR O N T V I E W
S ECT I O N A - A
DIMENSIONS IN MILLIMETRES
FIGURE E6 TYPICAL ISLAND HOOD TYPE 4 CANOPY
INCORPORATING GREASE-REMOVAL DEVICES
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Supply air
Exhaust air
300
m i n.
300
300
300
20 0 0 m i n.
Ty p i c a l ove n
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DIMENSIONS IN MILLIMETRES
FIGURE E7 TYPICAL PIZZA OVEN HOOD TYPE 3 CANOPY
INCORPORATING GREASE-REMOVAL DEVICES
Supply air
Exhaust air
300
m i n.
300
m i n.
300
m i n.
4 50 m i n.
Ty p i c a l
side-hinged
ove n
20 0 0 mi n.
DIMENSIONS IN MILLIMETRES
FIGURE E8 TYPICAL SIDE HINGED OVEN CANOPY HOOD TYPE 3
INCORPORATING GREASE-REMOVAL DEVICES
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Exhaust air
3 0 0 m i n.
3 0 0 m i n.
3 0 0 m i n.
3 0 0 m i n.
20 0 0 m i n.
Ty p i c a l
hood style
di s hwa s h e r
DIMENSIONS IN MILLIMETRES
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FIGURE E9 TYPICAL HOOD DISHWASHER STYLE CANOPY HOOD TYPE 3
Exhaust air
Exhaust air
Exhaust air
3 0 0 m i n.
3 0 0 m i n.
300
m i n.
300
m i n.
3 0 0 m i n. 3 0 0 m i n.
3 0 0 m i n.
20 0 0 m i n.
Ty p i c a l
c o nveyo r
style
di s hwa s h e r
DIMENSIONS IN MILLIMETRES
FIGURE E10 TYPICAL CONVEYOR DISHWASHER STYLE HOOD TYPE 6 CANOPY
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Supply air
Exhaust air
3 0 0 m i n.
3 0 0 m i n.
3 0 0 m i n.
4 50 m i n.
20 0 0 m i n.
Ty p i c a l
asian cooking
wo k
FIGURE E11 TYPICAL WOK STYLE HOOD TYPE 3 CANOPY
INCORPORATING GREASE-REMOVAL DEVICES
24 0 0 m m (mi n i m u m c e i l i n g h e i g h t)
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DIMENSIONS IN MILLIMETRES
FIGURE E12 TYPICAL VENTILATED CEILING HOOD TYPE 5 INCORPORATING
GREASE-REMOVAL DEVICES
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APPENDIX F
PERFORMANCE-ORIENTED APPROACHES TO MECHANICAL
VENTILATION SYSTEM DESIGN (INCLUDING SYSTEM COMPONENT
SELECTION)
(Informative)
F1 SCOPE
This Appendix sets out recommended procedures for the adoption of a performance-based
approach to mechanical ventilation system design and system component design or
selection.
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Such an approach may be considered appropriate or necessary where—
(a)
the level of contaminants in the outdoor air make it more desirable to treat the
outdoor air and/or recycle air and not use or reduce use of outdoor air for maintaining
indoor air quality;
(b)
the level of temperature or humidity of the outdoor air makes it more economical to
treat recycle air than to cool, heat, humidify or dehumidify outdoor air for
maintaining indoor air quality; or
(c)
exhaust air contaminant control may offer particular advantages (for example, exhaust
point location or the like).
A performance-based approach is one in which satisfactory air quality is maintained by
using alternative methods where prescriptive requirements of this Standard are complied
with.
A performance-based approach may be used in reference to particular pollutants (including
odour) where other pollutants are controlled by application of the prescriptive ventilation
approach specified in this Standard.
F2 DESIGN OBJECTIVES
The overall design objective should be the provision of an indoor or outdoor environment,
or both (as appropriate to the situation under consideration); that is at least equivalent to
that obtained by application of the prescriptive ventilation approach specified in this
Standard.
Component design/selection criteria should reflect the overall design objective.
Typical components are air-distribution systems/devices, particulate filtration systems/
devices and gas phase air-cleaning systems/devices.
The prescriptive procedure specified in this Standard provides an indirect solution to the
control of indoor contaminants or the appropriate emission of air contaminants to the
ambient atmosphere.
A direct solution should control the concentrations of contaminants to specified, acceptable
levels.
In the case of contaminants that may have an adverse effect on human health, acceptable
levels are those set or recommended by relevant health or pollution authorities.
In the case of odorous indoor air contaminants or airborne orinasal irritants, the design
objective is that the so affected air should be acceptable to at least 80% of unadapted
visitors to the space.
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Indoor air contaminants at concentration levels that cause ocular irritation, to reasonably
healthy people, are not permitted.
Air released to the ambient atmosphere should meet the overall objective stated above and
the requirements of relevant pollutant authorities.
Where more than one evaluation criteria is to be met, in respect of one contaminant or of a
group of contaminants, the most stringent criteria should determine compliance with this
Standard.
Criteria for general air quality contaminants should be appropriate to the relevant
environment, that is, they should be suited to—
(a)
workplace environment;
(b)
general community indoor environment;
(c)
the external environment; or
(d)
simultaneously, all or some of these environments, as appropriate.
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NOTES:
1 Quantitative assessment criteria, for certain indoor air contaminants, for application to the
workplace environment are available from OH&S authorities.
2 Quantitative assessment criteria for certain indoor air contaminants, for application to general
community indoor environments, is available from the National Health and Medical Research
Council, the National Environment Protection Council and international bodies. Assessment
criteria are not available for all known contaminants, and these concentration limits may not,
of themselves, ensure appropriate indoor air quality with respect to other contaminants.
Criteria selected for health-related contaminants should be to the approval of relevant
health authorities. Criteria for amenity purposes (e.g. odour nuisance) should comply with
the requirements of this Standard.
When odour filters, odour-masking devices/chemicals or similar devices are not used,
carbon dioxide (CO2) may be a useful indicator of body odour levels and occupancy
patterns.
NOTES:
1 In the event that CO 2 is controlled by any method other than dilution, the effects of the
possible elevations of other contaminants should be considered.
2 Carbon dioxide criteria should suit the populations and situations to which they are applied.
F3 PROPOSAL SUBMISSION AND APPROVAL
Specific design objectives should be proposed and should be in the form and detail
necessary for proper consideration.
A performance-oriented approach should be independently reviewed.
F4 AIR CONTAMINANTS
For the purposes of this Appendix air contaminants are of two types:
(a)
Type 1 contaminants.
(b)
Type 2 contaminants.
Type 1 contaminants are of a nature that their concentration in air may be determined by
means that do not require direct sensory evaluation by humans. Generally, particulates and
many single chemical species meet these criteria.
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Where an odorous/irritating substance must occur in high concentrations in order to be
perceived or where analytical techniques for its evaluation are particularly advanced and (in
both cases) there is a well-documented relationship between chemical concentration and
sensory effect then the substance may be proposed as a Type 1 contaminant. In this case
sufficient justifying information should be contained in the proposal.
Type 2 contaminants are of a nature that their concentration in air may only be determined
by means that require direct sensory evaluation by humans.
Where new proven instrumentation/analytical techniques are introduced and suitable
chemical concentration/sensory effect information is available, a Class 2 contaminant may,
in some circumstances, become a Type 1 contaminant.
F5 CONTROL OF CONTAMINANTS
F5.1 Type 1 contaminants
Type 1 contaminants, of particulate type, should be controlled by particulate arresting
devices such as gravity chambers, cyclones, electrostatic precipitators and filters.
Type 1 contaminants, of non-particulate type (i.e. gases) should be controlled by absorptive
devices, adsorptive devices and catalytic devices.
F5.2 Type 2 contaminants
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Type 2 contaminants are usually gaseous substances (i.e. not particulates) and should be
controlled by absorptive devices, adsorptive devices and catalytic devices.
Highly concentrated Type 2 contaminants may occur in particulate form, in which case,
they will usually be accompanied by the same contaminant in gaseous form. In such cases, a
range of control devices, in series, may be utilized.
F6 EVALUATION OF AIR QUALITY
F6.1 General
Air quality should be assessed in an occupied space or at the point where exhaust air is
discharged to atmosphere.
F6.2 Type 1 contaminants
Type 1 contaminants should be evaluated by recognized test methods, competently applied.
Where relevant health authorities specify or recommend particular test approaches, these
approaches should be applied. Otherwise, best available test approaches should be applied
in accordance with recognized best practice. All test approaches should be fit for purpose.
F6.3 Type 2 contaminants
F6.3.1 General
Type 2 contaminants (usually odours) should be evaluated by appropriate psychophysical
means.
Two forms of evaluation of Type 2 contaminants in occupied spaces are acceptable, as
specified in Paragraphs F6.3.2 and F6.3.3.
When Type 2 contaminants are evaluated, the space under consideration should be
operating at stable representative conditions of use and occupancy.
Ventilation lead and ventilation lag effects, as documented in this Standard, should be
absent in all spaces associated with the evaluation process.
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F6.3.2 Form 1 evaluation
In a Form 1 evaluation, the Type 2 contaminant in the occupied space should be evaluated
in direct relation to the fundamental criteria, that is, 80% acceptance by an unadapted test
panel.
Assessors should be outside for 5 min or more before entering the space that is to be
judged.
NOTE: Assessors should enter the space from the outside (i.e. not from another enclosure) in the
manner of a normal visitor and should render a judgement of acceptability within 15 s.
The outside place(s) of assembly of assessors should be outdoors and should not be subject
to significant odours (e.g. that of processes, exhausts or significant traffic fumes).
NOTE: Each observer should make the evaluation independently of other observers and without
influence from a panel leader.
F6.3.3 Form 2 evaluation
F6.3.3.1 General
In a Form 2 evaluation, the Type 2 contaminant in the occupied space is evaluated in
comparative relation to a contamination in another space, one normally occupied and
ventilated in accordance with the prescriptive requirements of this Standard (but not
over-ventilated, given the occupancy profile). An adapted or unadapted test panel may be
used.
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Thermal, humidity and other variations between the conditions in the various spaces should
not prejudice the evaluation.
F6.3.3.2 Principles
The following apply to Form 1 or Form 2 evaluations:
(a)
Assessors may enter spaces in order to evaluate Type 2 contaminants therein;
alternatively, air may be delivered from these spaces to a suitable evaluation point. In
the former case, assessors may use whatever time they require to make a decision.
NOTE: Assessors (panel members) may be trained or untrained.
(b)
Training should not prejudice the outcome.
(c)
Assessors should be prequalified for satisfactory olfactory detection and
discrimination in accordance with relevant Australian Standards or ISO Standards.
(d)
The panel size should be as necessary to give the required evaluation with not more
than 5% error probability but should be not less than 10 persons.
(e)
Assessment should follow ‘double blind’ principles.
(f)
The judgement of assessors should be expressed anonymously, in writing, by secret
ballot.
(g)
Ballot questions should not prejudice the outcome.
(h)
Results should be evaluated and expressed in accordance with statistical procedures
in accordance with relevant Australian Standards and ISO Standards.
(i)
Unless with express permission of the certifying or approving authority, assessors
should not have a direct or indirect interest in the outcome of the evaluation or of its
consequences.
F6.4 Variation of test approach
Test approaches involving the movement of airstreams to assessment stations may be
required. In such cases, the means of transfer should not prejudice the outcome by their
effect on air contamination or thermal quality; that is, ducting/piping/fans should not
significantly contaminate or remove contaminants from the air.
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F7 EVALUATION OF DEVICES AND SYSTEMS
Devices and systems should be evaluated by recognized test methods. Where relevant
health authorities specify or recommend particular test approaches for Type 1 contaminants,
these approaches should be applied. Otherwise, best available test approaches should be
applied in accordance with recognized best practice.
All test approaches should be fit for purpose.
Devices and systems will usually be best rated or specified in terms of fractional or
percentage efficiency of removal of contaminant from the airstream; that is, the
concentration of contaminant in the airstream leaving the device/system divided by the
concentration of contaminant in the airstream entering the device/system or (in percentage
representation) this number multiplied by 100.
The provisions of Paragraph F6 should apply to evaluations.
Conditions of test and application of devices and systems should be included in the
proposal (e.g. maximum/minimum airflows).
F8 MONITORING
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Provision for monitoring the indoor air quality in terms of its contaminants and basic
constituents may be necessary; particularly where the contaminants of concern have
significant health effect.
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APPENDIX G
RATIONALE FOR LAG OR LEAD TIME FOR TRANSIENT OCCUPANCY
(Informative)
G1 LAG TIME
When spaces such as classrooms, auditoriums or offices are unoccupied for several hours
and then occupied, operation of the ventilation system may be delayed to use the capacity
of the air in the space to dilute contaminants. This applies to cases where the inside
contaminants are associated only with human occupancy and where contaminants are
dissipated by natural means during long vacant periods. The operation of the ventilation
system can then be delayed until the concentration of contaminants reaches the acceptable
limit associated with the minimum ventilation requirements at steady state.
The concentration of any contaminant in the absence of ventilation (C) in a given space of
volume (v1), is expressed as follows:
Cθ 
N

v
. . . G(1)
where (N) is the contaminant generation rate, (v) is volume and () is time.
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The contaminant concentration (Cs) under a steady state condition with ventilation rate (V)
is expressed as follows:
Cs 
N
v
. . . G(2)
The maximum permissible ventilation delay time ( d) after the space is occupied is when C
equals Cs or—
d 
v
V
. . . G(3)
The equation is plotted in Figure 2.3 for various ventilation rates, in litres per second per
person and space volume in cubic metres per person.
G2 LEAD TIME
When contaminants are generated independent of people or their activities, and the
contaminants do not present a short-term health hazard, ventilation may be shut off during
unoccupied periods. In these cases, ventilation should be provided in advance of the time of
occupancy so that acceptable conditions will exist for people at the start of occupancy. It is
impracticable to operate the ventilation at the minimum requirement until steady-state is
reached, because this is approached asymptotically with time, and may take several hours to
reach practical equilibrium. An engineering estimate of a permissible contaminant level of
1.25 times the steady-state value has, therefore, been selected as the maximum level at the
time of occupancy. The occupants would, for a time, be subjected to somewhat higher
values of contaminant than the steady-state value. It is postulated that the factor of safety
implicit in the values given in Section 2 are adequate so that, for practical purposes, the
required ventilation amenity level is provided over the entire occupancy period.
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AS 1668.2—2012
When an initially contaminated room with a level of concentration (Ci) is diluted by a given
rate of ventilation (V2), the time required to lower the concentration to a fraction (X) above
the final steady-state concentration level may be expressed in terms of the ventilation lead
time (a) as follows:
a 
v  CiV / N   1 
ln

V 
X

a
= lead time, in hours
v
= room volume, in cubic metres
N
= contaminant concentration generation rate
V
= ventilation rate, in cubic metres per hour
Ci
= initial concentration
X
= 1.25  the steady state contamination level
. . . G(4)
where
Figure 2.4 is a plot of this relationship where Ci is assumed to be approximately 10 times
the steady-state value and X = 0.25 or 25%.
For enclosures of transient occupancy or enclosures that are under-ventilated, the time for
the enclosure to reach an upper acceptable limit may be determined as follows:
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
v
Vr  Va
. . . G(5)
where

= time before contamination reaches the upper acceptable limit, in hours
v
= volume of the enclosure, in cubic metres
Vr
= minimum outdoor air rate required by this Standard, in cubic metres per hour
Va
= actual outdoor air rate supplied to the space, in cubic metres
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AS 1668.2—2012
102
APPENDIX H
COMMENTARY ON CARBON MONOXIDE EXPOSURE IN OCCUPATIONAL
ENVIRONMENTS
(Informative)
H1 GENERAL CAR PARK
A1
Ventilation rates for occupational exposure in car parks are calculated on the revised
NOHSC exposure criteria. At the time of publication, the National Occupational Health and
Safety Commission (NOHSC) had set an 8 h time-weighted average exposure limit of
30 ppm (34 mg/m3) for CO. This ambient CO level over 8 h is equivalent to a
carboxyhaemoglobin (COHb) level of 5%. This COHb level is considered to be the current
acceptable risk that workers may be exposed to over a working lifetime of exposure. Those
individuals at a greater risk are those with cardiovascular disease, those with subclinical
cardiovascular disease and foetuses of exposed pregnant women. If NOHSC revises the
exposure criteria appropriate changes to the ventilation rates should be made.
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H2 EXPOSURE STANDARDS
Percentage blood COHb is dependent upon the ambient CO concentration, exposure
duration, ventilation rate (breathing), and pre-exposure COHb level, as the exposure limit
was established to correlate with 5% COHb, it is assumed that there is no additional
exposure to CO. There are three prominent sources of additional CO to which workers may
be exposed. Firstly, and most importantly exposure to tobacco smoke increases the COHb
levels. Cigarettes can increase the COHb level to 5–9% and cigars up to 20%. Smokers are
subject to the exposure limit established to protect non-smokers. Similarly, exposure to
methylene chloride (dichloromethane) increases the COHb percentage in the blood.
Methylene chloride is metabolized to CO and can be stored in the body providing a source
of continued exposure to CO after exposure to methylene chloride ceases. Exposure to
methylene chloride alone, at 100 ppm over a working day, should not raise the blood COHb
above 5%. Thirdly, endogenous production from some diseases, including haemolytic
anaemia, can increase COHb levels to 4–6%.
H3 SHORT-TERM EXPOSURES
The NOHSC expert working group are of the opinion that the application of short term
exposure limits (STELs) and general excursion limits (GELs) will not ensure that the 5%
COHb level is not exceeded. Consequently, it is imperative that excursions above the
exposure limit are stringently controlled to maintain an acceptable risk. With the removal of
the short term exposure limit (STEL), NOHSC has provided guidance on short-term
excursions above the exposure limit with the intention to maintain COHb levels below 5%
(see Table H1).
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AS 1668.2—2012
TABLE H1
SHORT-TERM EXCURSIONS PERMISSIBLE
ABOVE THE NOHSC CO-EXPOSURE LIMIT
Concentration, ppm
A2
Total exposure duration per day,
minutes
400
Not to be exceeded
200
15
100
30
60
60
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The total exposure duration per day represents the sum of exposures at this level over an 8 h
working day, assuming no additional exposure to CO. CO is very slowly released from the
blood (with a half-life in healthy people of approximately 4 to 5 h at rest) following
cessation of exposure. COHb levels gradually increase or decrease to reach the equilibrium
state depending on the initial percentage of COHb in the blood and the ambient CO
concentration. Thus, exposure to CO followed by a sufficient period of fresh air will reduce
COHb levels back to pre-exposure levels.
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AS 1668.2—2012
104
APPENDIX I
EXAMPLES OF LAYOUTS OF CAR PARK VENTILATION
(Informative)
Figures I1 to I4 provide some examples of car park mechanical ventilation layouts.
3
D i r e c t a i r p ath
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7 m a x.
Ag g r e g ate of a r e a s f u r th e r th a n 3 m
t h (s h ow n s h a d e d )
from d
dii r e c t a i r p a
ath
m u s t n ot exc e e d 10% of th e tot a l
a r e a of th e e n c l o s u r e
3
3
D i r e c t a i r p ath
3
7 m a x.
7 m a x.
NOTE: If register spacing exceeds 6 m, part of the car park between registers will be further than 3 m from direct air
path.
DIMENSIONS IN METRES
FIGURE I1 EXHAUST VENTILATION OF A ‘SQUARE’ CAR PARK
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 Standards Australia
105
AS 1668.2—2012
3
c
Dire
path
t air
3
pa
th
3
D
ir
ec
t
ai
r
Ag g r e g ate of a r e a s f u r th e r th a n 3 m
dii r e c t a i r p a
ath
from d
t h (s h ow n s h a d e d )
to n ot exc e e d 10% of th e tot a l a r e a
of th e e n c l o s u r e
3
3
3
pa
th
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3
Di
re
ct
air
3
DIMENSIONS IN METRES
FIGURE I2 EXHAUST VENTILATION VIA A SINGLE INTAKE
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AS 1668.2—2012
106
10 m m a x.
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A r e a s e r ve d by e a c h
s u p p l y r e g i s te r to n ot
exc e e d 50 m 2
FIGURE I3 SUPPLY VENTILATION OF A ‘SQUARE’ CAR PARK
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AS 1668.2—2012
3
D i r e c t a i r p a th
Ad di ti o n a l a i r
m ov i n g d ev i c e
in accordance
wi th 4.4. 2(c)
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O b s t r u c ti o n
f r e e zo n e
3
15°
7
D i s to r te d p a th
7 m a x.
3
DIMENSIONS IN METRES
FIGURE I4 EXHAUST VENTILATION OF A ‘SQUARE’ CAR PARK INCORPORATING
AN AIR MOVING DEVICE
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AS 1668.2—2012
108
APPENDIX J
BASIS OF AIRFLOW RATES FORMULAE FOR CAR PARKS
(Informative)
J1 FLEET AVERAGE CO EMISSION RATES ON COLD ENGINE START
First minute
25 g/min
Second minute
16 g/min
Third minute
10 g/min
Fourth minute
7 g/min
Fifth minute
5 g/min
Hot
3.2 g/min
It has been assumed that emission controls do not start functioning effectively until several
minutes after the engine has been in operation. Accordingly, the above figures are
independent of advancement in engine and emission control designs.
J2 AVERAGE CAR SPEED IN CAR PARK
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6 km/h (0.01 min/m).
J3 AMBIENT CO CONCENTRATION
Peak 9 ppm (based on NEPC and NHMRC standards and goals).
8 h, average 3 ppm.
J4 PARKING TIMES
The following times are used:
(a)
Parking—car drives at 6 km/h to space, and takes 1 min to park.
(b)
De-parking—car takes 0.5 min to leave space, and then takes 0.5 to 1.5 min to leave
zone.
(c)
Cars exiting from other areas are in the second minute of operation.
J5 CO CRITERIA
The formula aims for a 1 h average of 60 ppm (51 ppm rise) on the basis that it is
intended—
(a)
to ensure that peak concentrations for short periods do not exceed 100 ppm rise;
(b)
if CO monitoring devices are set to reduce ventilation when CO concentration drops
below 40 ppm to ensure that the 8 h average does not exceed 30 ppm;
(c)
to ensure that the eight-hour average does not exceed 30 ppm; and
(d)
to limit percentage blood COHb to 5% for car park users.
A2
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AS 1668.2—2012
J6 FORMULAE
For a typical commercial car park, peak movements occur at morning and evening peak
hours, when 50% of the total car spaces may be filled or emptied within 1 h. Generally, the
evening peak hour generates more CO as the cars start cold so, for most car parks, the exit
hour produces the highest requirement. Due to the effect of engine temperature on vehicle
contaminant generation rates, it is not necessary to consider the requirement of vehicle
entry.
J7 DERIVATION OF FORMULAE
The following applies:
(a)
Contaminant generation rate Equation 4.4.4.1 CO generated per car movement on
exit—
A2
 n1  0.5 min @ 25 g/min  0.5   25  16    n1d1  0.01 min/m  16 g/min
n2 d 2  0.01 min/m  16 g/min
= 17n1 + 0.16n 1d 1 + 0.16n 2d2
= 0.17 (100n1 + n1d1 + n2d 2)
grams CO
0.872  0.17 (100n1 + n1d 1 + n2d2)
litres CO
Required air quantity for 51 ppm rise, P car exit movements per car space per hour—
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A2
P  0.872  0.17  100n1  n1d1  n2 d 2  
106
L/s
51  3600
P  0.807  (100 n1  n1d1  n2 d 2 )
[factor rounded to 0.85, for Equation 4.4.4.2].
(b)
Minimum air quantity Based on one engine operating at 12.1 g/min (30 min cold
start average for older cars) for 91 ppm rise (to 100 ppm)—
Required air quantity=
0.872  12.1  106
91  60
= 1932 L/s, say 2000 L/s
J8 BASIS OF TABLE 4.1
Values obtained for some commercial parking stations indicate the following:
(a)
(b)
Example 1: 865 car spaces.
(i)
Peak entry movement occurring in 9th hour ........................ 425 entries (4 exits).
(ii)
Peak exit movements occurring in 18th hour ....................... 317 exits (6 entries).
Example 2: 900 car spaces.
(i)
Peak entry movement occurring in 9th hour ...................... 284 entries (13 exits).
(ii)
Peak exit movements occurring in 18th hour ...................... 273 exits (28 entries)
For Example 1:
Entry peak hour = 0.496
Exit peak hour
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= 0.373
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AS 1668.2—2012
110
For Example 2:
Entry peak hour = 0.33
Exit peak hour
= 0.33
The table nominates 0.5 as the commercial parking usage factor.
J9 BASIS OF AREA MINIMUM
The minimum air quantity of 3.5 L/s per square metre has been reduced, in the same
proportion as other rates to—
3.5  0.85
 2.5
1.2
J10 BASIS FOR STAFF EXPOSURE FACTOR (TABLE 4.3)
The 8 h time weighted-average exposure limit for CO set by NOHSC for occupational
health and safety applies to occupants who stay in car parks for extended periods, resulting
in a higher ventilation requirement. At the time of publication, the exposure limit is 30 ppm
CO. For an average ambient concentration of CO of 3 ppm, the required air quantity for
27 ppm rise, P car exit movements per car space per hour
 P  0.872  0.17  (100n1  n1d1  n2 d 2 ) 
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A2
106
L/s
27  3600
P  1.525  100 n1  n1d1  n2 d 2 
which compares to the formula used in Clause 4.4.4 for car parks with no occupants who
stay in the car park for extended periods = P  0.85  100n1  n1d1  n2d 2  .
Hence, the staff exposure factor = 1.525/0.85= (rounded to 1.8).
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AS 1668.2—2012
APPENDIX K
BASIS FOR LENGTH OF VEHICLE QUEUE IN CAR PARKS
(Informative)
K1 CAR PARKS WITH PAY BOOTHS
For car parks, the ventilation equation assumes n LP cars attempt to exit through each lane in
1 h at peak (see Clause 4.6). Consider two criteria—
(a)
the build-up for the whole peak hour—
n LP  B = number of cars in queue
where
B = the number of cars a pay booth can process in 1 h; and
(b)
the build-up for a 10 min period with the rate at double the 1 h peak rate—
(2n LP – B)/6 = number of cars in queue.
If a pay booth can process one car every 20 s, B = 180, then for a commercial car park
(P = 0.5), we obtain results as follows:
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A2
nL
500
400
300
200
150
n LP
250
200
150
100
75
n LP – 180
70
20
—
—
—
cars length at the end of 1 h
1/6 (2 n LP – B)
53
37
20
3
—
cars length at the end of 10 min
[2.2n LP – 200]
350
240
130
20
—
m length
Below n L = 450, n LP = 225, the criteria 1/6(2 n LP – 180) is the highest.
Above n L = 450, the rate given by the ventilation equation is close to the rate specified for
exit lanes.
Therefore, use the expression 1/6(2nLP – 180).
In arriving at the rate for exit lanes, we have assumed 6.5 m length per car.
Therefore, the length of queue = 6.5  1/6(2nLP – 180)
= (2.17n LP – 195) m
= round to (2.2 round to (2.2n LP – 200) m
K2 CAR PARKS WITHOUT PAY BOOTHS
Using same approach, but assume rate of exit to street is the criterion.
For light traffic, 1 exit per 10 s  B
= 360  2.2n LP – 400
For heavy traffic, 1 exit per 20 s  B = 180  2.2n LP – 200
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AS 1668.2—2012
112
APPENDIX L
DERIVATION OF AIRFLOW RATES FOR QUEUING AREAS IN CAR PARKS
(Informative)
L1 EXIT LANES
Based on fleet average emission rate for 5th minute = 5 g/min.
For 51 ppm rise:
Required air quantity
0.875  5  106
=
51  60
= 1425 L/s
Assume 6.5 m per car in queue.
A1
Required air quantity per metre
= 219 L/s (say 225 L/s)
L2 ENTRY LANES
Based on hot engine emission rate for 5th minute = 3.2 g/min.
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For 51 ppm rise:
Required air quantity
=
0.875  3.2  106
51  60
= 912 L/s
Assume 6.5 m per car in queue.
Required air quantity per metre
= 140 L/s (say 150 L/s)
L3 DIESEL VEHICLES
Assume length per vehicle rises in same proportion as airflow required per vehicle.
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113
AS 1668.2—2012
APPENDIX M
AUTOMATIC MONITORING SYSTEMS FOR CAR PARKS—MARKING,
COMMISSIONING, RELIABILITY AND RECORDS
(Informative)
M1 MARKING
The supplier of the monitoring system should provide a durable label on the external
surface of each cabinet containing an analyser to be fixed in a conspicuous position with—
(a)
the words ‘SERVICE FREQUENCY’ in legible style upper case letters with a letter
height of not less than 8 mm, in a colour contrasting to the background; and
(b)
a number indicating the service frequency in months.
The number should be legible, 20 mm high and clearly visible. The service frequency
should be that period during which the supplier guarantees the system will, without
maintenance, report analytical results in accordance with Clause 4.12.3.
M2 COMMISSIONING
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Every monitoring system should be commissioned in accordance with the manufacturer’s
recommendations by a competent person, and calibrated with calibration gas whose
composition is certified by a qualified laboratory.
M3 RELIABILITY
Every monitoring system installed in enclosures should be operated and maintained so as to
maintain its reliability.
Re-calibration should be effected by a qualified person(s) at frequencies not greater than the
service frequency period, using calibration gas certified by a qualified laboratory.
M4 RECORDS
All calibrations, re-calibrations and related test work should be recorded, with the dates and
names of persons conducting the work and kept available at the operating site for
inspection.
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AS 1668.2—2012
114
APPENDIX N
PERFORMANCE APPLICATION TO CAR PARK VENTILATION
(Informative)
N1 PERFORMANCE APPLICATION
Ventilation systems should ensure that concentrations of atmospheric contaminants within
the enclosure do not exceed occupational or community exposure limits listed in this
Appendix. Ventilation should be provided to satisfy the minimum ventilation requirements.
Paragraphs N2 to N4 provide means to satisfy the minimum ventilation requirements.
N2 MECHANICAL VENTILATION
Mechanical ventilation may be by means of supply air, exhaust air or a combination of
supply and exhaust air via openings complying with Clause 4.4.2 with a flow rate not less
than the minimum ventilation requirement calculated in accordance with Clause 4.4.3 or
Clause 4.4.4.
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N3 MIXED VENTILATION
Mixed ventilation is a combination of natural ventilation and mechanical ventilation. Those
areas provided with natural ventilation are required to comply with AS 1668.4. Those areas
provided with mechanical ventilation have to comply with Clause 4.4 and provided with
mechanical supply and exhaust. Both the supply and exhaust ventilation rates have to be not
less than the required ventilation rate calculated in accordance with Clause 4.4.3 or
Clause 4.4.4.
N4 OTHER ARRANGEMENTS
A2
A2
Any other arrangement may be used, provided it is demonstrated to limit the CO
concentration, between 750 mm and 1800 mm above the floor, less than—
(a)
60 ppm 1 h maximum average;
(b)
100 ppm 30 minute maximum average; and
(c)
30 ppm (TWA) 8 h.
N5 BASIS FOR EXPOSURE LIMITS
This Appendix recognizes the need to protect the health of both the general public and the
workers. In its preparation, the recommendations of authorities such as the National
Occupational Health and Safety Commission (NOHSC), the National Environment
Protection Council (NEPC) and the National Health and Medical Research Council
(NHMRC) were considered.
Ventilation rates are calculated on the following exposure criteria available at the time of
publication:
(a)
A1
NOHSC has set an 8 h time-weighted average exposure limit of 30 ppm (34 mg/m3)
for CO.
The NOHSC ambient CO level over 8 h is equivalent to a COHb level considered to
be the current acceptable risk that workers may be exposed to over a working lifetime
of exposure.
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 Standards Australia
115
(b)
AS 1668.2—2012
The NEPC and NHMRC has set a 9 ppm exposure limit for 8 h. This exposure limit is
approximately equivalent to a predicted 5% COHb level, which relates to a 60 ppm
exposure limit for an hour or a 100 ppm exposure limit for 30 min (both equivalent to
a predicted COHb level of 2%).
Systems designed in accordance with this Standard are based on a 9 ppm ambient CO level
and a 51 ppm rise in CO for non-occupied car parks or on a 3 ppm 8 h average ambient CO
level and a 27 ppm rise in CO for attendant parking or other occupied situations.
This Appendix assumes an ambient CO level of 9 ppm. Where data from the relevant EPA
or from site monitoring indicates a consistently lower ambient value, then that value may be
used in calculations.
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For enclosures for which a combination of natural ventilation and mechanical ventilation is
used, the effective mechanical airflow rate is the lesser of the supply airflow rate and the
exhaust airflow rate, as excess make-up air drawn from naturally ventilated areas may be
fully loaded with contaminants, and excess supply air may reduce the effectiveness of the
natural ventilation openings.
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AS 1668.2—2012
116
APPENDIX O
LOCAL EXHAUST VENTILATION REFERENCES
(Informative)
Table O1 provides a list of some Standards that may cover additional ventilation
requirements for specific applications.
TABLE O1
A2
APPLICABLE AUSTRALIAN STANDARDS AND RELEVANT CODES
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Title
Applicable Standard
Pressurized rooms or pressurized enclosures
AS 2380.4
Vented cells
AS 2676.1
Confined spaces
AS 2865
The storage and handling of gases in cylinders
AS 4332
Electrical equipment for explosive atmospheres—Protection by ventilation—
Type of protection v
AS 1482
The storage and handling of flammable and combustible liquids
AS 1940
Fume cupboards
AS/NZS 2243.8
Code of practice for handling combustible dusts
AS 4745
Gas installations—General installations
AS/NZS 5601.1
AS 4114.1
The storage and handling of organic peroxides
AS 2714
Stationary source emissions
AS 4323 series
Methods for sampling and analysis of ambient air
AS/NZS 3580 series
Model Code of Practice—Spray Painting and Powder Coating
Safe Work Australia—
Code of Practice
Model Code of Practice—Welding Processes
Model Code of Practice—Abrasive Blasting
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AS 1668.2—2012
BIBLIOGRAPHY
AS
1055
1055.1
A2
A2
1482
Electrical equipment for explosive atmospheres—Protection by ventilation—
Type of protection v
1668
1668.3
1668.4
The use of ventilation and airconditioning in buildings
Part 3: Smoke control systems for large single compartments or smoke
reservoirs
Part 4: Natural ventilation of buildings
1940
The storage and handling of flammable and combustible liquids
2107
Acoustics—Recommended design sound levels and reverberation times for
building interiors
2380
Electrical equipment for explosive atmospheres—Explosion-protection
techniques
Part 4: Pressurized rooms or pressurized enclosures
2380.4
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Acoustics—Description and measurement of environment noise
Part 1: General procedures
2714
The storage and handling of hazardous chemical materials—Class 5.2 substances
(organic peroxides)
2865
Confined spaces
3780
The storage and handling of corrosive substances
4332
The storage and handling of gases in cylinders
AS/NZS
2243
Safety in laboratories
2243.8
Part 8: Fume cupboards
3000
Electrical installations—(known as the Australian/New Zealand Wiring Rules)
3500
3500.1
Plumbing and drainage
Part 1: Water services
3666
3666.1
Air-handling and water systems of buildings—Microbial control
Part 1: Design, installation and commissioning
4745
Code of practice for handling combustible dusts
5601
5601.1
Gas installations
Part 1: General installations
HB
260
Hospital acquired infections—Engineering down the risk
ISO
7730
Ergonomics of the thermal environment—Analytical determination and
interpretation of thermal comfort using calculation of the PMV and PPD indices
and local thermal comfort criteria
ACGIH
American Conference of Governmental Industrial Hygienists
Industrial Ventilation: A Manual of Recommended Practice
AS 1668.2—2012
118
ASHRAE
55
Thermal Environmental Conditions For Human Occupancy
ASHRAE Handbook—Fundamentals
DIN
18869
Equipment
(all parts)
for
commercial
Australian Design Rules
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VDI
2052
Ventilation equipment for kitchens
kitchens—Components
for
ventilation
119
AS 1668.2—2012
AMENDMENT CONTROL SHEET
AS 1668.2—2012
Amendment No. 1 (2013)
CORRECTION
SUMMARY: This Amendment applies to the Preface, Clauses 3.3.1, 4.3.1, Equation 4.11.2 and
Appendices D, H, L and N.
Published on 1 October 2013
Amendment No. 2 (2016)
REVISED TEXT
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SUMMARY: This Amendment applies to Clauses 1.6, 2.2, 2.8.2, 2.8.4.1, 2.8.4.2, 3.3.1, 3.3.2.4, 3.4.1, 3.4.2.3,
3.4.4, 3.10.4, 4.2.1, 4.2.2, 4.4.2, 4.9, 4.11.1, 4.11.3, 5.3.3, 5.4.1, 5.4.2, 5.4.3, 5.4.4, 5.7, 5.7.1, 5.7.2, and 5.7.3;
Appendices A, B, D, E, H, J, K, N and O, and the Bibliography .
Published on 21 December 2016.
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AS 1668.2—2012
120
NOTES
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