DEPARTMENT OF DEFENCE
DEFENCE ESTATE QUALITY MANAGEMENT SYSTEM
MECHANICAL ENGINEERING
MICROBIAL CONTROL IN AIR HANDLING AND WATER
SYSTEMS OF DEFENCE BUILDINGS
August 2012
DOCUMENT STATUS
Version No.
Issue Date
1
2
3
4
May 2012
July 2012
Aug 2012
Aug 2012
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Amendment Details
Draft for review and comment
Review comments incorporated
DEMP review comments incorporated
Version issued for publish
Amended
by
TML
TML
TML
TML
August 2012 version 4
CONTENTS
1.0 INTRODUCTION
1.1
1.2
4
Aim
Sponsor
4
4
2.0 POLICY OBJECTIVES AND PRINCIPLES
2.1
2.2
5
Policy Objectives
Policy Principles
5
5
3.0 APPLICATION
6
4.0 STANDARDS GUIDELINES AND CODES OF PRACTICE
7
4.1
4.2
Standards Codes Regulations and Legislation
Guidelines and Application Manuals
5.0 DEFINITIONS
7
7
9
6.0 LEGIONELLA BACTERIA
11
7.0 MICROORGANISM MANAGEMENT AND CONTROL
13
8.0 COOLING WATER SYSTEMS
14
8.1
8.2
8.3
8.4
8.5
8.6
8.7
Approach to Maintenance
Prescriptive Maintenance Requirements
Performance-Based Maintenance Requirements
Existing Equipment Upgrade
Intermittent and Seasonal Equipment Use
Start-Up and Shut-Down Instructions
Retention of Records
9.0 WATER SYSTEMS
9.1
9.2
9.3
14
14
15
17
17
17
18
19
General
Water Treatment Products
Proprietary Water Treatment Devices
19
19
20
10.0 AIR HANDLING SYSTEMS
21
10.1 General
10.2 Prescriptive Maintenance Requirements
10.3 Performance-Based Maintenance Requirements of Air Handling
Systems
21
21
21
11.0 CERTIFICATION
23
12.0 REPORTING OUTBREAKS AND HIGH RISK EVENTS
24
13.0 DECONTAMINATION CLEANING AND DISINFECTION
25
14.0 GUIDANCE
27
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1.0 INTRODUCTION
Microorganisms are present in almost every environment found on earth including
within buildings. Microorganisms are normally present in relatively low concentrations
within buildings and are found on surfaces and on airborne dust and aerosol
particles.
The primary purpose of this Defence policy is to:
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Assist in the control of microorganisms in systems provided for Defence
buildings which are associated with health hazards such as the bacterial
genus Legionella. This bacterial genus can cause infections which lead to
Legionnaires' disease, hypersensitivity pneumonitis, humidifier fever and
Pontiac fever.
Assist in the control of other heterotrophic microorganism sources which can
lead to health hazards, such as Pseudomonas (e.g. causing skin rashes or
ear infections), amoebic meningitis, herpes, Chlamydia and gastro-intestinal
infections.
Reinforce and support Defence’s commitment to compliance with its
obligations under Work Health and Safety (WHS) legislation.
1.1
Aim
This policy aims to assist achieving Defence’s objectives and principles by providing
general and specific guidance on microbial control in air-handling and water systems
of Defence buildings.
1.2
Sponsor
This document is sponsored by Directorate of Estate Engineering Policy (DEEP) on
behalf of the Technical Authority Assistant Secretary Environment and Engineering
(ASEE). Enquiries may be directed to:
Director Estate Engineering Policy
Brindabella Park (BP-2-B049),
Canberra ACT 2600
Tel: (02) 6266 8178 Fax: (02) 6266 8211 Email: DSG - ID Engineering Policy
@defence.gov.au
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2.0 POLICY OBJECTIVES AND PRINCIPLES
2.1
Policy Objectives
This policy provides general and specific guidance on matters which shall be
considered by Service Providers in relation to microbial control in air-handling and
water systems provided for Defence buildings, to assist Defence achieve its
compliance objectives.
2.2
Policy Principles
The principles described in this document shall be used in implementing the policy
objectives.
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3.0 APPLICATION
The policy described in this document shall apply to Defence buildings which include:
 Cooling water systems as described in SAA/SNZ HB32 and defined in
AS/NZS 3666.1:2011.
 Air-handling systems in buildings excluding refrigerated room airconditioners.
 Condensate drainage equipment and air filters for non-ducted split system
airconditioners.
 Air conditioning plant.
 Evaporative cooling, evaporative condenser and closed-circuit cooling
systems.
 Humidifying systems.
 Water storage systems associated with potable water, fire sprinkler systems,
and irrigation.
 Hot, warm and cold water supply systems.
 Heated pools, spa pools and hydrotherapy pools.
 Cooling water systems for refrigeration equipment and air compressors,
industrial heat exchangers, spray irrigation systems, industrial type fluid
cooling systems.
The sources of legionellae which have generally been implicated in worldwide
outbreaks of Legionnaires’ disease have been identified with air conditioning systems
and cooling water systems which have been incorrectly commissioned or
inadequately maintained. Consequently, Defence Estate Management, Defence
personnel and Defence Service Providers shall be aware of their responsibilities and
duty of care obligations associated with design, supply, installation, commissioning,
operation, cleaning and maintenance of air-handling and water systems in order to
eliminate the health risk associated with microorganism infections.
This policy and related standards apply to all existing, new and replacement Defence
plant. The policy shall be read in conjunction with:
 DEQMS Work Health and Safety.
 Commonwealth legislation.
 Relevant State and Territory legislation.
 Regulatory authority requirements.
The term ‘buildings’ as used in this policy in phrases such as ‘air-handling and water
systems of buildings’ shall be read as also applying to Defence facilities and
installations other than buildings where air-handling and water systems are installed
independently of buildings. Such applications may be part of Defence industrial,
process, testing or similar applications.
For the purpose of this Defence policy:
 ‘Shall’ indicates a mandatory policy statement.
 ‘Should’ indicates a policy recommendation.
 ‘May’ indicates a course of action that is permissible; and the existence of an
option.
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4.0 STANDARDS GUIDELINES AND CODES OF
PRACTICE
4.1
Standards Codes Regulations and Legislation
Microbial management and control for Defence buildings shall comply with all
applicable standards, codes, regulations and legislation including but not limited to
the following.
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The Work Health and Safety (WHS) Act 2011.
WHS Regulations and WHS Safety Codes of Practice.
National Construction Code (NCC) Volume One – Building Code of Australia
(BCA).
AS 1657:1992 Fixed platforms, walkways, stairways and ladders – Design,
construction and installation.
AS 1668.2-1991 The use of mechanical ventilation and air-conditioning in
buildings. Mechanical ventilation for acceptable indoor-air quality.
AS/NZS 1715:2009 Selection, use and maintenance of respiratory protective
devices.
AS/NZS 1716:2012 Respiratory protective devices.
AS 2610.1-2007 Spa pools – Public spas.
AS/NZS 2865:2009 Confined spaces.
AS 3498 - 2009 Authorization requirements for plumbing products - Water
heaters and hot-water storage tanks.
AS/NZS 3666:2011 Air-handling and water systems of buildings - Microbial
control.
Part 1: Design, installation and commissioning.
Part 2: Operation and maintenance.
Part 3: Performance-based maintenance of cooling water systems.
Part 4: Performance-based maintenance of air-handling systems (ducts and
components).
AS/NZS 3500 Plumbing and drainage.
Part 1: Water services.
Part 4: Heated water services.
AS/NZS 3896:2008. Waters—Examination for Legionella spp. including
Legionella pneumophila.
AS 3979-2006 Hydrotherapy pools.
AS/NZS 4276 Water microbiology.
State and Territory statutory laws and related codes of practice and
guidelines.
4.2
Guidelines and Application Manuals
The following documents provide relevant guidance.
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Defence Safety Manual (SAFETYMAN).
Defence Incident Report Form AC 563. To be used in the event of an incident
or accident and available through DEQMS Support, OH&S, Forms.
SAA HB9 - 1994, Handbook – Occupational personal protection.
SAA/SNZ HB32:1995 Control of microbial growth in air-handling and water
systems in buildings.
National Environmental Health Forum Monographs. Water Series No. 1.
Guidance for the control of Legionella. 1996.
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AIRAH Application Manuals. DA17 – Cooling Towers. DA18 – Water
Treatment. DA 19 HVAC&R Maintenance, DA26 – Indoor Air Quality.
ASHRAE Handbook – HVAC Applications. Chapter: Water Treatment.
AIRAH Best Practice Guidelines – HVAC Hygiene.
Guidance material provided by Comcare.
Guidance and mandatory requirements of safety data sheets provided for
water treatment chemicals and biocides.
ASHRAE Guideline 12-2000. Minimizing the Risk of Legionellosis Associated
with Building Water Systems.
ANSI/ASHRAE Standard 188P: Prevention of legionellosis associated with
building water systems.
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5.0 DEFINITIONS
For the purpose of this policy the following definitions apply.
Automatic Bleed-Off Equipment
Equipment which removes water from a system to limit the concentration of total
dissolved solid and suspended solids.
Automatic Dosing Equipment
Equipment which automatically doses cooling water systems with biocides and water
treatment chemicals to control microbial growth, corrosion, scaling, fouling and the
build-up of solids.
Biofilm
A layer of microorganisms formed as a thin slime on surfaces in contact with water.
Cooling Water System
A heat exchange system comprising heat-generating plant, water-based heat
rejection plant and interconnecting recirculating pipework and associated pumps,
valves and controls.
Cycles of Concentration
The degree of concentration of the dissolved solids of the cooling system make-up
water as a result of the evaporation that takes place in the cooling tower.
Dead-leg
A section of a water-based system that does not permit the circulation of water.
Drift
Water lost from a cooling tower, evaporative condenser or similar equipment as liquid
droplets entrained in the discharge air. This excludes condensation.
Drift Eliminators
Inertial moisture droplet stripping devices fitted to cooling towers and evaporative
condensers to remove moisture droplets entrained in the discharge air.
Evaporative Air-Cooling Equipment
A device that effects a reduction of the dry bulb temperature of air by evaporating
water into air.
Evaporative Condenser
A heat exchanger in which refrigerant is cooled by a combination of air movement
and water spraying.
Heterotrophic Microorganisms
Microorganisms that obtain nourishment by digesting plant or animal matter, as
opposed to photosynthesizing food, as plants do.
High Risk Event
An event that could reasonably be expected to significantly or adversely affect public
health.
Humidifier Fever
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A form of allergic reaction caused by inhalation of allergens of microbial origin arising
from the wetted surface of equipment, such as humidifiers.
Hypersensitivity Pneumonitis
Respiratory illness usually caused by inhalation of the spores or antigens of various
different types of microorganisms.
Key Performance Indicator
A risk factor that is identified as testable, assessable and controllable for the
performance, monitoring and verification of the system.
Legionnaires’ Disease
A potentially fatal illness characterised by pneumonia and cause by infection with
Legionella bacteria species, commonly L.pneumophila. All infections caused by
Legionella species are covered by the general term ‘legionellosis.’ (Legionnaires
disease is a notifiable disease in each State and Territory).
Pontiac Fever
A self-limiting, short-duration, non-fatal fever caused by Legionella bacteria.
Regulatory Authority
Any authority that is authorised by statute to exercise jurisdiction over matters such
as the design, materials, installation, commissioning, operation or maintenance of
any part of an air-handling or water system, plant, equipment or systems covered by
this policy.
Significant Modification
A modification to a warm water or air handling system falling within the meaning of
AS/NZS 3666 that directly affects the hazard potential of the equipment.
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6.0 LEGIONELLA BACTERIA
Legionella bacteria are widespread in nature and can be found in a variety of
environments including most fresh water, natural and constructed water sources,
fresh or brackish water, coastal waters, mud and soil, in potting mixes and in
compost. Consequently, it is to be expected that Legionella bacteria will be present in
building air-handling and water systems.
Legionella thrives in particular environments, which are outlined below:
 In warm water Legionella bacteria:
Remain dormant at low temperature and growth below 25ºC is rare.
Multiply in the temperature range of 20ºC to 45ºC with the optimum range
being 35ºC to 37ºC.
Growth ceases above 45ºC and the bacteria dies with increasing rapidity as
temperature rises above 45ºC.
Are killed by long exposure at 50ºC temperature and by shorter exposure at
higher temperatures.
Are killed almost instantly at 70ºC.
 The presence of sediment, sludge, scale and organic material act as nutrient
sources and provide a surface for attachment.
 Some materials, such as natural rubber used for tap washers, are a known
nutrient source. Care is required in their use and application.
 Presence of waterborne microorganisms, such as algae, amoebae and other
bacteria can provide nutrient sources.
 Algal slimes provide a stable environment for growth.
 The bulk of the microbial population in any water system is present in the
biofilms which cover all wetted surfaces. On these surfaces, traces of nutrient
are absorbed and aggregate and thereby sustain those passing microbes
which settle and adhere to them. A biofilm is built up comprising a mixed
population of interdependent microbial species embedded in a matrix which
supports and protects them. Legionella has been shown to be a biofilm
organism and thrives in biofilm. Consequently, biofilm formation can protect
legionellae from concentrations of biocide that would otherwise kill or inhibit
growth.
 Dead legs in piping systems (i.e. sections of the system that do not allow
water circulation) provide niches for growth.
 Temperature stratification in calorifiers can provide locations suited to
legionellae growth.
 The growth of the bacteria is very responsive to the presence of iron and zinc
such as occurs in unprotected, rusting galvanised iron construction material in
wet cooling tower environments.
 The presence of oxygen and carbon dioxide.
In their natural environments legionellae obtain their requirements for growth and
proliferation (i.e. cell division) through interactions with other microorganisms such as
algae, protozoa and other bacteria, and by the utilisation of organic and inorganic
material.
Legionellae are parasitic and can infect freshwater amoebae and multiply within
them. The persistence of legionellae within amoebae provides a means for dispersal
and survival in ambient air conditions which would normally kill them. Amoebae can
also protect parasitic legionellae from disinfection.
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Legionellae also proliferate within biofilms, within other microorganisms and their byproducts and within matter entrained in water systems.
Design, installation, operation and maintenance of air-handling and water systems for
Defence buildings shall consider the above matters when establishing appropriate
control measures against microbial growth including Legionella bacteria.
New and replacement equipment and systems shall be selected, designed,
manufactured, installed and operated on the basis of eliminating environments which
are susceptible to the uncontrolled growth and proliferation of Legionella bacteria.
Consideration shall be given to associated factors such as the location of the
equipment and systems, construction materials, and maintenance requirements
including provisions for cleaning and water quality monitoring.
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7.0 MICROORGANISM MANAGEMENT AND
CONTROL
Defence Manager Estate and Facilities Services (MEFS) shall ensure that Service
Providers responsible for the maintenance of air-handling and warm water systems
develop and keep current, compliant plans for the management and control of
microorganisms in the maintained systems. Plans shall include appropriate
maintenance and operation instructions that are to be recorded in the Garrison and
Estate Management System (GEMS).
Maintenance Service Providers shall ensure management and control of microbial
growth are in full compliance with the requirements of regulatory authorities, State
and Territory Health Departments, and local municipal authorities.
Maintenance and operating instructions shall as a minimum comply with the
requirements of:
 The above authorities.
 The applicable requirements of the Standards and documents covered under
clause 4.0.
Maintenance instructions shall include mandatory procedures for the use of personal
protective equipment, for handling of chemicals and for working in confined spaces.
Microorganism management and control shall allow for the possible development of
microbial resistance to specific biocides and biocide formulations. Service Providers
shall regularly alternate biocides to reduce the risk of resistant strains of
microorganisms being developed.
Care shall be taken in the use of biocides, cleaning agents and any other chemicals
in air-handling equipment such as humidifiers, spray coils and evaporative air cooling
equipment. Chemicals may be hazardous to health when entrained in the airstream.
Suppliers’ recommendations, including safety data sheets and other information shall
be followed to ensure the proper use of chemicals.
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8.0 COOLING WATER SYSTEMS
8.1
Approach to Maintenance
The biological process of rapid growth of Legionella bacteria in water systems to high
concentrations is essential before the water systems are considered potentially
hazardous and capable of causing the serious and potentially fatal illness
legionellosis. Consequently, effective control of the growth process is fundamental to
addressing the potential hazard and this is achieved by effective maintenance and
compliance with applicable legislation, codes, standards and regulatory authority
requirements.
The design of water systems shall facilitate maintenance, cleaning, control of
microbial growth, and minimising drift from the heat rejection plant. This shall be
achieved by compliance with the applicable requirements of Clause 4 Standards,
Guidelines and Codes of Practice.
Parts 2, 3 and 4 of AS/NZS 3666:2011 include prescriptive and performance-based
approaches to maintenance of air-handling and water systems of buildings. Defence
presently requires a prescriptive-based approach to maintenance of cooling water
systems where the maintenance actions are prescribed and in accordance with
AS/NZS 3666.2:2011. However, in some situations a performance-based approach
may be necessary for reasons described under 8.3 below. Where a performancebased approach is required for a specific Defence system AS/NZS 3666.3:2011 shall
apply and associated water quality management and testing regimes shall be in
place and strictly followed. Under the performance-based approach Defence relies
upon the expertise of Service Providers to assess and recommend the most
appropriate approach to maintenance for a particular application based on their
professional experience and technical competence.
Irrespective of the prescriptive or performance-based approach to maintenance, in
the event of an outbreak of Legionnaires’ Disease or water sampling results that
identify actionable microorganism quantities (for legionellae or heterotrophic
microorganisms as determined by AS/NZS 3666.3:2011 Tables 3.1, 3.2) immediate
notification to Defence is required together with special action as determined by the
Standard and as advised by the local health authorities.
8.2
Prescriptive Maintenance Requirements
Section 2 of AS/NZS 3666.2:2011 covers a prescriptive approach to operation and
maintenance of air-handling and water systems of buildings. Clause 2.5 describes a
prescriptive approach to maintenance of cooling water systems. Typically, Service
Providers should follow this approach where systems can be shut down without
adversely affecting Defence capability, continuity of service or process, or the
Defence facility being served.
The prescriptive maintenance requirements of AS/NZS 3666.2:2011 Section 2
includes minimum inspection and cleaning periods which in the case of cooling water
systems is inspection at least monthly and cleaning as necessary with intervals not
exceeding six months.
For evaporative coolers the Standard’s inspection requirement is at least every three
months. However, regular cleaning and draining is considered to be the most
appropriate means of microbial control for evaporative coolers and industry
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experience has shown that a frequency of three-monthly cleaning is inadequate in
some Australian localities and some applications. Consequently, local conditions
such as excessive dust, construction activities, excessive ambient conditions and the
like, may necessitate a shorter maintenance frequency. In exceptional situations
such as dusty and windy conditions this frequency may need to be weekly.
Service providers shall fully consider the local site conditions and ambient weather
when determining and recommending maintenance frequencies.
Maintenance frequencies shall be reviewed for effectiveness by the Service Provider
on an ongoing basis during the maintenance period and shall be adjusted to more
frequent maintenance if determined necessary by maintenance experience. All such
adjustments shall be in full consultation with Defence. In no circumstances shall
maintenance be reduced to less frequent maintenance than stated in AS/NZS
3666.2:2011.
8.3
Performance-Based Maintenance Requirements
The prescriptive approach to maintenance of water systems described in AS/NZS
3666.2:2011 is not appropriate for critical Defence systems which cannot be shut
down for regular cleaning. In this situation Service Providers shall follow the
performance-based maintenance approach in accordance with AS/NZS 3666.3:2011
for cooling water systems.
The primary aim of this approach is preventive by nature, i.e. to avoid conditions
occurring in cooling water systems which may allow microorganisms including
legionellae to multiply and thereby cause a health risk. This is achieved by:
 effective, methodical management of a system’s water quality which includes
monthly cooling water sampling and assessment for the presence of
legionellae,
 creating hygienic conditions, and
 automatically regulating water treatment and monitoring, assessment and
control strategies.
Health is a principle outcome of the performance-based approach.
Risk assessments for Defence cooling water systems shall be undertaken every five
years or as otherwise directed by the MEFS. Assessments shall be carried out by
practicing engineers in accordance with AS/NZS 3666.3:2011 Clause 2.3 Risk
Assessment. (Defence requirements for a ‘practicing engineer’ are stated under
clause 11.0 Certification). Risk assessments shall include a determination of the
criticality of the Defence system whereby a critical cooling water system is one which
cannot be shut down for regular cleaning due to Defence capability, continuity of
service, security or similar considerations.
Existing risk assessments shall be revised if:
 There are reasons to believe that the findings of the original assessment are
no longer valid;
 System monitoring reveals the need for preventive or corrective action;
 Significant change has occurred in the local environment, in local work
practices or in equipment;
 Construction work is proposed, or has commenced in the vicinity of the
cooling water system.
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Copies of the risk assessment report shall be submitted to the MEFS, to the
regulatory authority, and to Comcare (upon request). A copy of the risk assessment
report shall be incorporated into the Operation and Maintenance (O&M) manual, the
site water treatment manual and GEMS.
AS/NZS 3666.3:2011 Table 2.1 ‘Risk Factors to be Assessed and Controlled’ shall
be assessed and documented for each individual system (i.e. for each cooling water
system rather than each overall Defence facility). Key performance indicators
identified in Table 2.1 shall be monitored and controlled in accordance with AS/NZS
3666.3:2011 Section 3 ‘Performance monitoring and control.
AS/NZS 3666.3:2011 Table 3.1 describes the required control strategies for the
presence of legionellae whilst Figure 3.1 describes the associated assessment and
control process. Similarly, Table 3.2 describes the required control strategies for the
presence of other heterotrophic microorganisms whilst Figure 3.2 describes the
associated assessment and control process. These control strategies and
assessment and control processes shall be followed when using the performance
based approach to maintenance. If in doing so, additional operation and maintenance
requirements are identified, they shall be included in the maintenance Service
Provider’s management and control plans in consultation with Defence.
The initial risk assessment of a cooling water system shall be carried out as part of
the implementation of the Standard to the installation or as required by the regulatory
authority. For a new installation, initial risk assessment shall commence during the
design stage and be reviewed during initial operation of the completed installation.
The risk assessment reports and control measures shall be recorded in the project
records and incorporated into the Operation and Maintenance (O&M) manual, the
site water treatment manual and GEMS.
The management of system water quality is an important strategy in minimising
health risks associated with cooling water systems. Automatically regulated water
treatment systems shall be provided for cooling water systems for effective
management of corrosion, scaling, fouling and microbial growth. The effectiveness of
water quality management systems and water treatment shall be assessed by the
Service provider in accordance with ASNZS 3666.3:2011 Clause 3.4. Assessment
frequency shall be at least monthly when the cooling water systems are in use.
The temperature of the operating cooling water systems shall be monitored and
assessed in accordance with AS/NZS 3666.3:2011 Clause 3.5 Water Temperature.
Assessment frequency shall be at least monthly when the cooling water systems are
in use.
AS/NZS 3666 advises that the available data for outbreaks of legionellae infections
indicate that most outbreaks are associated with a concentration of 1,000 cfu/mL
(colony forming units per millilitre) or greater and that disease may be associated
with lower levels. Consequently, the intent of AS/NZS 3666 is for cooling water
systems to operate with non-detectable concentrations of legionellae.
Under the performance-based maintenance approach examination for the presence
of legionellae shall be carried out monthly in accordance with AS/NZS 3896:2008 by
a NATA accredited laboratory. A control strategy shall be immediately initiated in
accordance with AS/NZS 3666.3:2011 Clause 3.2 whenever a detectable
concentration of Legionella is found, where ‘detectable’ is defined as 10 cfu/mL or
greater. Where higher concentrations are detected, a more demanding control
strategy is required, as determined by Table 3.1 AS/NZS 3666.3:2011.
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Similarly, under the performance-based maintenance approach examination for the
presence of heterotrophic microorganisms shall be carried out monthly by a NATA
accredited laboratory in accordance with AS/NZS 3666.3:2011 and AS/NZS
4276.3.1:2007 or AS/NZS 4276.3.2:2003 as applicable. A control strategy shall be
immediately initiated in accordance with AS/NZS 3666.3:2011 Clause 3.3 and Table
3.2 whenever a heterotrophic colony count (HCC) is ≥100,000 cfu/mL.
8.4
Existing Equipment Upgrade
The following cooling water system equipment shall be upgraded without delay if
identified as non-compliant with the relevant requirements of the standards, codes,
regulations and legislation identified in Clause 4.1. The completed upgrade shall be
certified by a practicing engineer. (Refer to clause 11.0 Certification)
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Drift eliminators. These are a vital piece of equipment for minimising the risk
of Legionnaires’ disease outbreaks due to cooling water systems. They also
help to retain the chemically treated water in the systems. For specific
requirements refer to AS/NZS 3666.1:2011 Clause 4.4 Drift Control and to the
regulatory authority. Upgrades to eliminators may increase air flow resistance
through the cooling plant and thereby reduce the heat rejection capacity.
Consequently, Service Providers shall assess the impact on system
performance and heat rejection capacity and shall advise Defence
accordingly before the replacement is undertaken.
Automatic cooling water bleed-off equipment.
Automatic cooling water chemical and biocide dosing equipment.
8.5
Intermittent and Seasonal Equipment Use
Where a cooling water system has been out of operation for a period of more than 30
days an assessment shall be carried out in accordance with AS/NZS 3666.3:2011
3.6 Start Up. This requires the actions of clauses 3.2 to 3.5 of the standard to be
carried out within 3 to 7 days of the system recommencing operation.
Where a cooling water system is shut down without being drained, the water
treatment program shall be maintained until the system is returned to normal use.
AS/NZS 3666.2:2011 clause 2.5.4 requires cooling water to be circulated through the
entire system at intervals of not greater than once every 48 hours. This is a maximum
interval which Defence requires to be appropriately reduced to circulate corrosion
inhibitors and biocides where the local environment, local work practices or adjacent
construction activities adversely affect the cooling water system or encourage
microbial growth.
A cooling water system that is typically on stand-by or used as a back-up system
shall be operated for a minimum period of one hour per week to circulate corrosion
inhibitors and biocides. The minimum one hour period may need to be increased by
Service Providers in situations where the local environment, local work practices or
adjacent construction activities adversely affect the cooling water system or
encourage microbial growth.
8.6
Start-Up and Shut-Down Instructions
All Defence cooling towers, evaporative condensers and similar cooling water
equipment shall have written start-up and shut-down instructions prominently
displayed on or near to the plant. The instructions shall be clear, concise, and simple
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to follow and shall be protected from weathering. The instructions shall include full
(normal and emergency) contact details of:
 The maintenance Service Provider.
 The water treatment Service Provider.
 The regulatory authority with jurisdiction over the installation.
 The building owner or owner’s representative.
8.7
Retention of Records
All records of cooling water system treatment, inspections, maintenance and testing
shall be prepared, retained and made readily available for inspection in accordance
with Defence requirements and those of regulatory authorities and AS/NZS
3666.3:2011 Clause 3.7 Results and Records. The records provide evidence of
compliance and as such shall be retained in a legible form for a minimum period of 7
years.
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9.0 WATER SYSTEMS
9.1
General
For the purposes of this policy document hot and warm water are defined in
accordance with AS/NZS 3666.1:2011 as follows:
 Hot water is water at or above 60ºC.
 Warm water is water between 30ºC and 60ºC (nominally 43ºC).
Hot, warm and cold water systems shall be designed to avoid conditions likely to
encourage the growth of legionellae. In addition to complying with the relevant
requirements of the standards, codes, regulations and legislation identified in Clause
4.1, the guidance provided in the document ‘Guidance for the control of Legionella –
National Environmental Health Forum Monographs – Water series no. 1’ shall be
considered by Service Providers.
9.2
Water Treatment Products
Defence requires water treatment product literature and safety data sheets (SDSs) to
be included in the building’s water treatment service manual, the O&M manual, and
to be readily available on site to anyone who could be exposed to the product. SDSs
shall comply with Work Health and Safety Regulations 2011:
 Chapter 7. Hazardous chemical. Part 7.1 Hazardous chemicals. Division 2
Obligations relating to safety data sheets and other matters.
 Schedule 7 Safety Data Sheets.
The relevant information, requirements and instructions in the SDSs shall be followed
whenever the water treatment product is being handled, stored, used and disposed
of. All water treatment products used and their labelling, packaging, storage and user
instructions shall comply with all applicable legislation and regulatory authority
requirements.
Appropriate safety signs shall be permanently exhibited in Defence building locations
where hazardous water treatment products (i.e. chemicals, biocides and other similar
toxic materials) are handled, stored, used and disposed of. Safety signage shall
comply with AS 1319-1994 ‘Safety signs for the occupational environment’ and,
where necessary, the ‘Globally Harmonised System for the Classification and
Labelling of Chemicals’ (GHS).
Evidence of compliance with Defence policy together with authorisation or
certification by the relevant regulatory authority shall be included in the water
treatment service manual and the site O&M manual. The evidence shall confirm that
the water treatment products, when used in the full range of required concentrations
and combinations for effective treatment, comply with the relevant regulations which
restrict hazardous effluents in the air and waste water drainage systems.
Where a system’s cooling water is drawn from a source other than cold water mains
(i.e. a lake, cooling pond or where grey water is use), alternative water treatment
considerations and strategies will be involved. These shall be documented and
applied based on past experience and relevant information.
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9.3
Proprietary Water Treatment Devices
Conventional treatment of cooling water systems achieves microbial control through
the use of biocides and water treatment chemicals. Proprietary devices of a nonchemical type are available to the HVAC industry as an alternative to conventional
water treatment. However, these should not be used without substantiation of their
claimed effectiveness and a thorough understanding of the technical aspects of the
processes involved.
Two of the common non-chemical water treatment alternatives are:
Metallic Ions
This alternative releases silver or copper ions into the cooling water via
electrochemical means to control bacterial growth. Some chemical water treatment is
still required for the treatment to be effective. Major concerns with this alternative are:
 The potential for copper ion deposition on steel and aluminium surfaces within
the cooling water system and subsequent galvanic corrosion.
 Limitations placed by water treatment authorities on the discharge of cooling
water systems containing copper and silver ions.
Ultraviolet Irradiation
This alternative process involves killing microbes in the circulating cooling water by
exposing them to ultraviolet radiation. However, this is not effective for cooling water
systems where all of the microorganisms cannot be exposed to the treatment. This
situation arises because:
 The ultraviolet irradiation process leaves no residual material in the water to
kill microbes which are remote from the ultraviolet light source.
 Sessile microbes (i.e. microbes that are permanently attached to the internal
surfaces of the cooling water system rather than floating in the water) and
microbes that do not pass the ultraviolet light source are not affected by the
process.
 Effective water treatment systems must be able to control biofilms which
attach around the internal surfaces of the complete water circuit, remote from
the ultraviolet light source.
Any form of water treatment for Defence buildings shall be tried and tested and
proven effective rather than relying on unsubstantiated claims by manufacturers and
suppliers. (Substantiation requires independent laboratory and field trial testing plus
verification with credible supporting evidence).
Proprietary water treatment devices and systems shall not to be used for Defence
buildings unless proven effective by credible evidence which is submitted to DEEP
for review and assessment prior to installation.
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10.0 AIR HANDLING SYSTEMS
10.1 General
Guidance on the control of microbial growth in air-handling systems is provided in the
following:
 SAA/SNZ HB32:1995 Control of microbial growth in air-handling and water
systems of buildings
 AIRAH Application Manual No. DA26 – Indoor Air Quality.
 AS/NZS 3666:2011 Parts 2 and 4. These standards cover prescriptive and
performance-based maintenance approaches for air-handling systems of
buildings which are also aimed at controlling microbial growth.
Defence relies upon the expertise of Service Providers to assess and recommend
the most appropriate approach to maintenance for a particular application based on
their professional experience and technical competence.
Air-handling system filters: Attention is drawn to the requirements of AS/NZS
3666.1:2011 Clause 2.4 with regards to air handling system filters having a minimum
20% efficiency when tested with test dust No. 1 and a minimum 85% arrestance
when tested with test dust No. 4, in accordance with AS 1324.2.
10.2 Prescriptive Maintenance Requirements
AS/NZS 3666.2:2011 Clause 2.3 describes prescriptive maintenance requirements
for air-handling systems. Equipment covered includes:
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Outdoor air intakes and exhausts.
Air filters.
Humidifiers.
Evaporative air-cooling equipment.
Ducts and components, the latter including coils, trays and sumps,
condensate drains, fans, terminal units, supply air outlets, return and relief air
grilles.
10.3 Performance-Based Maintenance Requirements of
Air Handling Systems
AS/NZS 3666.4:2011 addresses the performance of maintenance programs and is
required to be read in conjunction with AS/NZS 3666.1:2011, and the relevant
clauses of AS/NZS 3666.2:2011. The objective of the standard is to provide a
performance-based approach to the maintenance of hygienic conditions with airhandling systems of buildings.
AS/NZS 3666.4:2011 covers a performance-based risk management methodology
for maintenance. This verifies control of contamination sources to ensure air-handling
systems provide acceptable air quality and meet the same level of maintenance
described by the prescriptive requirements of the standard. Whilst performance
based maintenance of air-handling systems in Defence buildings shall generally be
carried out to the requirements of AS/NZS 3666.4:2011, Service Providers shall
incorporate the WHS Act’s approach to risk elimination into the methodology
described in the standard.
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AS/NZS 3666.4:2011 describes microbial monitoring, assessment and control
strategies in terms of key performance indicators which are carried out in accordance
with the Standard’s Table 2.1 ‘Risk Factors to be Assessed and Controlled.’
Section 2 of this Part of the standard ‘Identification and Assessment of Risk Factors’
lists risk factors that contribute to the growth and dissemination of microorganisms
within air-handling systems and clause 2.3 describes a risk assessment method to be
undertaken.
Appendix A of this Part of the standard covers ‘Risk Characterization’ which sets out
a procedure for tabulating the assessments for each identified risk category. Risk
characterization includes the following key concepts as described in the standard.
‘Likelihood
Assessing the likelihood of an identified problem becoming worse than before
the next planned maintenance visit, rated from ‘insignificant’ to ‘catastrophic.’
Consequence
The significance of adverse conditions or events, rated from ‘almost certain’ to
‘rare.’
Inherent risk level
A qualitative assessment of the risk as a result of determinations of
consequence and likelihood, rated from ‘low’ to ‘extreme.’
Control mechanism
A fortuitous or planned means of controlling or reducing the risk.
Residual Risk
The final outcome for each risk category.’
The approach described above is based on the concept of risk characterization and
risk reduction to a target residual level. It is important for Defence Service Providers
to apply the WHS Act’s due diligence approach to performance based maintenance
which first and foremost aims to eliminate risk rather than minimising it to a target
residual risk.
Where the risk assessment process for performance-based maintenance does not
eliminate an identified risk, it is important to document the justification for elimination
not being achieved and the considerations of the other control methods in order of
the hierarchy.
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11.0 CERTIFICATION
Practicing engineers shall certify to Defence, compliance of the microbial control
provisions of all new or modified existing air-handling and water systems provided for
Defence buildings, with the requirements of AS/NZS 3666:2011 and other applicable
Codes and Standards. Copies of the written certification shall be submitted to the
Project Director, the MEFS, the regulatory authority and to GEMS. Copies may be
provided to Comcare upon request. A copy shall be provided in the O&M manual and
the water treatment manual.
For the purpose of this policy document, a practicing engineer is one registered with
the National Professional Engineers Register (NPER) and registered to practice in
the areas of Mechanical Engineering or Building Services Engineering. In addition,
Defence requires such engineers to have the qualifications and experience to
evaluate the condition of the complete cooling water system. They shall be
competent, practicing, appropriately qualified and appropriately experienced.
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12.0 REPORTING OUTBREAKS AND HIGH RISK
EVENTS
Legionellosis is a reportable disease under State and Territory Health Acts. MEFS
shall ensure their maintenance Service Providers, Project Managers, Contract
Managers and the like who are responsible for the installation and maintenance of
air-handling and water systems are aware of their legal obligations for reporting high
risk microbial events.
Maintenance Service Providers, Project Managers, Contract Managers and the like
shall inform themselves of their statutory obligations for reportable, communicable
diseases such as legionellosis, Pseudomonas, amoebic meningitis, gastro-intestinal
infections etc.
The MEFS shall notify the State or Territory Health Department, regulatory authority
and Comcare within 24 hours of:
 receiving a test result of Legionella bacteria concentration ≥ 1,000 cfu/mL; or
 after receiving a test result of heterotrophic colony count ≥ 5,000,000 cfu/mL;
or
 any other high risk event; or
 as otherwise required by State of Territory Health Departments or the
regulatory authority;
and confirm and enact the required measures to prevent an outbreak of illness.
The above events are classified by Defence as dangerous incidents (i.e. high risk
events) and shall be notified in accordance with the procedures in the Defence WHS
Incident Report AC563.
Defence MEFS shall keep their WHS representatives informed of all microbial testing
results (including low and high risk events) and all measures taken to assure that airhandling and water systems are well maintained and operating in a safe, hygienic
and compliant condition. In the event of high risk events they shall fully inform their
WHS representatives about actions taken to eliminating the risk, and provide full
details of subsequent test results.
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13.0 DECONTAMINATION CLEANING AND
DISINFECTION
It is not the intent of this policy to detail procedures for decontaminating, cleaning and
disinfecting air-handling and water systems. These procedures are adequately
covered by existing Standards and expert literature and are also subject to continuing
change as knowledge and experience of treatment methodologies grows. It is also
recognised that regulatory authorities, State and Territory Health Departments and
local municipal authorities, may have their own specific procedures.
Guidance on decontamination, cleaning and disinfection is provided by State and
Territory Codes of Practice, by local health authorities, and in the following
documents:
 AS/NZS 3666.3:2011 Appendix B. On-line Disinfection Procedure for
Cooling Water Systems.
 AS/NZS 3666.3:2011 Appendix C. Decontamination Procedures for Cooling
Water Systems.
 National Environmental Health Forum Monographs. Water Series No. 1.
Guidance for the control of Legionella. 1996. Clause 10.1.4 Cleaning and
Disinfection. Clause 10.1.6 Decontamination.
 ACT Health Code of Practice 2005. Cooling Towers, Evaporative
Condensers and Warm Water Storage Systems. Appendix C. Warm water
storage system cleaning and disinfection.
 SAA/SNZ HB32:1995 Control of microbial growth in air-handling and water
systems of buildings. Clause 6.12. Decontamination.
Guidelines for the use of personal protective equipment during commissioning of
cooling water systems are provided in Appendix A of AS/NZS 3666.1:2011.
Defence policy requirements are:
 Decontamination, cleaning and disinfection procedures shall be acceptable to
the applicable regulatory authorities. They shall be determined and specified
by the design Service Provider during system design; confirmed by the
installation Service Provider upon completion of the installation; included in
the O&M Manual and the site water treatment service manual; and provided
readily available at the site installation for immediate reference. The
procedures shall be reviewed annually and maintained current by the
maintenance Service Provider.
 Decontamination, cleaning and disinfection shall be carried out in accordance
with the requirements of the applicable regulatory authorities.
 Appropriate safety precautions shall be taken during decontamination,
cleaning and disinfection. Personal protective clothing and equipment shall be
used where hazardous chemicals are stored and where used in the
decontamination, cleaning and disinfection process.
 All work shall be carried out by and supervised by appropriately licensed,
experienced and competent persons.
 Emergency decontamination, cleaning and disinfection shall be carried out
upon occurrence of a high risk event or when directed by the regulatory
authority or by Defence.
 Appropriate records of all decontamination, cleaning and disinfection events
shall be recorded in the site maintenance log book, provided to the MEFS and
recorded as otherwise required by the regulatory authority and Defence.
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
All duties, responsibilities and reporting requirements associated with
maintenance of air-handling and water systems at Defence buildings shall be
clearly defined and diligently carried out. (Outbreaks of legionellosis have
occurred in situations where engineering solutions were appropriate but
definitions of duties were unclear and reporting procedures were poor).
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14.0 GUIDANCE
General guidance on minimizing the risk of microbial growth in air-handling and water
systems is described in this clause for information purposes. The guidance is based
on Defence and industry experience and is included in this policy document to
reinforce good practice and compliance. The guidance is not intended to be fully
comprehensive or to replace the professional expertise and competence required of
Defence Service Providers when exercising their due diligence for legislation, code
and policy compliant outcomes under their WHS duty of care obligation.
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Incoming cold water supplies should be protected against heat gains which
may inadvertently increase the water temperature to 30ºC or more.
Heat gain to reticulated and stored cold water should be avoided.
Hot water systems should be of the pressure mains type and thermostatically
set to 60ºC or greater.
Large central hot water systems with long runs should incorporate
recirculating pumps to ensure the temperature of the water in the reticulation
systems and storage tanks is maintained above 60ºC.
New or extended cold water storage tank systems should be cleaned and
disinfected before commissioning, in accordance with AS/NZS 3500.1.
New or extended hot water systems should be operated and maintained in
accordance with AS/NZS 3500.4.
Cooling tower fans and the condenser water pumps should continue to
operate for a period after the thermal plant has shut down so that hot
condenser water can be cooled to below 25ºC (or preferably below 20ºC) to
minimize microbial growth.
Cooling tower fans should commence operation before condenser water flows
through the tower and should continue to operate for a period of time after
shutdown of condenser water flow. This strategy ensures that condenser
water is passing through the cooling tower only when the rated air quantity
passes through the drift eliminators and thereby minimizes condenser water
drift.
Where duplicate (duty/standby) condenser water pumps are provided, the
installation and controls should automatically change over the duty and
standby pumps on a regular basis to avoid stagnant water and microbial
growth in the standby pump and associated pipework.
High legionellae concentrations are most likely to occur in small cooling water
systems rather than large systems due to their high wetted surface area
relative to a small water volume. (Wetted surface area affects sediment
deposition and biofilm development). Consequently, small cooling water
systems may require greater care and attention than larger systems.
The multiplication of legionellae occurs preferentially at the warm surfaces of
systems such as piping and heat exchangers rather than in the heat rejection
plant (i.e. in cooling tower basins) which contain the coldest water in the
systems.
Water heaters and hot-water storage tanks should comply with AS 3498 2009 Clause 7 Control and Protection sub-clause 7.1 (j) for the means to
inhibit the growth of Legionella bacteria in potable water within the waterheating appliances.
The following water systems should be maintained, cleaned and inspected as
required by the local water authority, AS/NZS 3500.1 and SAA/SNZ HB 32.
- All cold water storage and cold water feed tanks and systems associated
with potable water systems.
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- All water storage tanks and systems associated with fire sprinkler systems.
- All water storage tanks and systems (including grey water) associated with
irrigation systems.
Combined storage tanks for potable water and fire services present a risk of
cross-contamination and should be avoided in accordance with AS/NZS
3666.1:2011.
Condensate and Equipment Drainage: Plant rooms that are air-plenums (i.e.
used for air handling system outdoor air supply or part of the return air path)
should comply with AS/NZS 3666.1:2011 clause 2.9 including Notes 1, 2 and
3, requiring sealing of associated drains and traps.
Cooling water systems provided for Defence buildings should not include
dead-legs, as required by AS/NZS 3666.1:2011 clause 4.1.3.
Cooling tower balance (equalising) pipes should be designed to prevent
formation of dead-legs and to ensure effective water treatment.
Mechanical services drawings should clearly show on plan views and
elevations, the respective locations of existing and proposed heat rejection
plant (evaporative cooling equipment, cooling towers, evaporative condensers
etc) and building openings (air intakes, exhaust outlets, natural ventilation
openings, lift shaft vents etc). When locating such plant and openings,
Service Providers should avoid cross-contamination and should consider the
effect of prevailing wind directions, wind effects, multiple roof levels and
arrangement of adjacent structures.
Regular routine operation and maintenance should be carried out on airhandling and water systems. AS/NZS 3666.2:2011 Section 2 details
minimum requirements which for some systems (i.e. coils, trays, drains,
tundishes and sumps etc) involves monthly inspection, checking and
cleaning.
Easy and safe access should be provided for inspection, maintenance and
cleaning of plant, equipment and components covered by this policy. The
relevant requirements of associated Standards should be complied with
including AS 1470, AS 1657, AS/NZS 1892 Parts 1 and 5 and AS/NZS 2865.
Access to heat rejection plant (i.e. cooling towers, evaporative condensers
etc) should be controlled and limited to those associated with provision,
operation and maintenance of the systems. This may necessitate fencing with
locked access gates. ‘Authorised Access Only’ signs should be provided.
Warning signs should be provided to discourage people from gathering in the
vicinity of heat rejection plant.
Care should be taken in the use of chemicals (biocides, cleaning agents etc)
in air-handling equipment such as evaporative coolers, humidifiers, spray
coils and the like where residual chemicals are directly exposed to the
airstream and may present a health hazard. Manufacturers’
recommendations, including SDSs shall be followed to ensure the proper use
of such chemicals.
Automatic dosing equipment should incorporate a lock-out function which
prevents biocides and water treatment chemicals from being injected into the
cooling water while the automatic bleed-off to drain is operating.
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Microbial Control in Air Handling and Water Systems