HVAC | Slide 1 of 31
WHO Technical Report Series,
No. 937, 2006. Annex 2
May 2006

HVAC
To continue from Part 1(a), now focus on:
 Air filtration
 The role of HVAC in dust control
 HVAC system design and its components (part 2)
 Commissioning, qualification and maintenance (part 3)
HVAC | Slide 2 of 31 May 2006

HVAC
Air Filtration
 Degree of filtration is important to prevent contamination
 Type of filters to be used dependent on the quality of ambient air, return air and air change rates
 Manufacturer to determine, select and prove appropriate filters for use considering level of ambient air contamination, national requirements, product specific requirements
4.2.1, 4.2.3
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HVAC
Levels of protection and recommended filtration
Recommended filtration Level of protection
Level 1 Primary filters, e.g. EN779 G4*
Level 2 and 3
Level 2 and 3
Production area with 100% outside air: Primary plus secondary filter (e.g. EN779 G4 plus F8 filters)
Production area with recirculated plus ambient air with a risk of cross-contamination: Primary plus secondary plus tertiary filter (e.g. EN779 G4 plus F8 plus EN1822 H13 filters)
*Filter class should be referenced to the standard test method
4.2.1
HVAC | Slide 4 of 31 May 2006

HVAC
Contamination should be prevented through appropriate:
 Materials for components and construction
 Design and appropriate access to dampers, filters and other components
 Personnel operations
 Airflow direction
 Air distribution component design and installation and location
 Type of diffusers (non-induction type recommended)
 Air exhaust (normally from a low level)
4.2.4
– 4.2.10
HVAC | Slide 5 of 31 May 2006

HVAC | Slide 6 of 31 May 2006
HVAC

HVAC
Filtered air entering a production room or covering a process can be

 turbulent, or unidirectional (laminar)
 GMP aspect
 economical aspect
Other technologies: barrier technology/isolator technology .
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HVAC
Turbulent dilution of dirty air
Unidirectional/laminar displacement of dirty air
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Airflow patterns
HVAC
Prefilter
AHU
Main filter
1
Turbulent
HVAC | Slide 9 of 31 May 2006
2
Unidirectional
3
Turbulent

HVAC
Workbench (vertical) Cabin/booth Ceiling
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HVAC
Unidirectional airflow (UDAF) :
Provided where needed over product or material to prevent contamination, or to protect operator
UDAF in weighing areas
 The aim is to provide dust containment
 Airflow velocity should not affect balance
 Position of material, balance, operator determined and validated – no obstruction of airflow or risk
4.3.1 – 4.3.10
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HVAC
HVAC | Slide 12 of 31 May 2006
Annex 5, 7.

HVAC
HVAC | Slide 13 of 31 May 2006
Annex 5, 7.

HVAC
 Facilities normally under positive pressure to the outside
 Prevent infiltration of unfiltered, contaminated air from outside
 Some cases - negative pressure (e.g. penicillin manufacture). Special precautions to be taken
4.4.1
– 4.4.4
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HVAC
Cross-contamination
 General aspects and concepts
 Displacement concept
– low pressure differential, high airflow
 Pressure differential concept
– high pressure differential, low airflow
 Physical barrier concept
HVAC | Slide 15 of 31 May 2006
4.5

HVAC
General aspects
 Multiproduct OSD manufacturing, prevent movement of dust between areas where different products are processed
 Directional air movement and pressure cascade can be helpful – dust containment
 Normally, corridor at higher pressure than cubicles, cubicles at higher pressure than atmosphere
4.5.1
– 4.5.3
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HVAC
Containment concepts
 Pressure cascade regime influenced by:
– Product and product group, e.g. highly potent products (in some cases, pressure cascade regime negative to atmosphere)
– Processing methods
 Building structure should be considered including airtight ceilings and walls, close fitting doors, sealed light fittings
4.5.4
– 4.5.9
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HVAC
Displacement concept
 Air supplied to the corridor, through the doors (grilles) to the cubicles
 Air extracted at the back of the cubicle
 Velocity high enough to prevent turbulence in doorway

Requires large air quantities
( Not preferred method)
4.5.10 – 4.5.12
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HVAC
Pressure differential concept
 Concept can include high pressure differential, low airflow, and airlocks in the design
 Airlock types include: Cascade, sink and bubble type
 Sufficient pressure differential required to ensure containment and prevent flow reversal – but not so high as to create turbulence
 Consider effect of other items such as equipment and extraction systems in cubicles
 Operating limits and tolerances 4.5.13 – 4.5.18,
4.5.22
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HVAC
Pressure differential concept (2)
 Calibrated monitoring devices, set to alarm system
 Monitoring and recording of results
 Doors open to higher pressure
 Dust extraction system design
– Interlocked with air-handling system
– No airflow between rooms linked to same system
– Room pressure imbalance
4.5.19 – 4.5.26
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HVAC
Pressure cascade solids
Protection from cross-contamination
Room 1
15 Pa
Room 2
15 Pa
Room 3
15 Pa
Air Lock Air Lock
30 Pa
Passage
E
HVAC |
Note : Direction of door opening relative to room pressure
Slide 21 of 31 May 2006
Air
Lock
15 Pa
0 Pa

HVAC
 In some cases, impervious barriers are used to prevent cross-contamination
 Spot ventilation
 Capture hoods
4.5.27 – 4.5.28
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HVAC
Temperature and relative humidity (RH)
 Controlled, monitored and recorded where relevant
 Materials and product requirements, operator comfort
 Minimum and maximum limits
 Premises design appropriate, e.g. low humidity areas, well sealed and airlocks where necessary
 HVAC design – also prevent moisture migration
4.6.1.
– 4.6.6
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HVAC
Temperature and relative humidity (RH) (2)
 Remove moisture, or add moisture as necessary
 Dehumidification
– Refrigerated dehumidifiers with cooling media
– Chemical dehumidifiers
 Humidifiers should not be sources of contamination
– Use of pure steam or clean steam
– No chemicals added to boiler system if these can have a detrimental effect on product (e.g. some corrosion inhibitors/chelating agents)
4.6.7. – 4.6.11
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HVAC
Temperature and relative humidity (RH) (3)
Humidification systems: Design should be such that the system does not become the source of contamination:
 No accumulation of condensate
 Avoid evaporative systems, atomizers, water-mist sprays
 Suitable duct material, insulation of cold surfaces
 Air filters not immediately downstream of humidifiers
 Chemical driers – used if not sources of contamination
4.6.12. – 4.6.18
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HVAC

Dust and vapour removed at source
 Point of use extraction – fixed points or movable hood – plus general directional airflow in room
 Ensure sufficient transfer velocity to prevent dust settling in ducting
 Risk analysis – airflow direction, hazards, operator
5.1.
– 5.7
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HVAC
 Normally air supplied through ceiling diffusers, and air extracted from low level – aids flushing effect
 Extraction of vapours – consider density of vapour
 Handling harmful products – additional steps needed
– e.g. barrier technology, glove boxes
– totally enclosed garments with air-breathing systems
 Fresh air rate supply
– comfort, odour and fume removal, leakage, pressure control, etc.
5.8.
– 5.14
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HVAC
Protection of the environment (Exhaust air dust)
 Exhaust air from equipment and some areas of production carry heavy loads of dust (e.g. FBD, coating, weighing)
 Filtration needed to prevent ambient contamination
 Not highly potent material
– EN779 F9 filter recommended
 Harmful substances (e.g. hormones)
– EN1822 H12 (HEPA) filter recommended
– In some cases two banks of HEPA filters
– Safe change filter housings ("bag-in bag-out" filters)
6.1.1 – 6.1.5
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HVAC
Protection of the environment (Exhaust air dust) (2)
 Filter banks provided with pressure differential indication gauges
 Limits indicated, results monitored at regular intervals
– Manual, Building Management Systems, Building
Automated Systems, System Control and Data Acquisition systems

Automated systems provided with alarm or similar system to indicate OOS
6.1.6 – 6.1.10
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HVAC
Protection of the environment (Exhaust air dust) (3)
 Reverse pulse dust collectors
– Should be equipped with cartridge filters with compressed air lance,
– Continuous operation – no interruption of airflow
 Dust collectors with mechanical shakers
– Used in a manner not to become source of contamination
–
Switched off at times resulting in loss of airflow, and disruption of pressure cascade
 Wet scrubbers
– Use suitable drainage system for dust slurry 6.1.11
– 6.1.15
 Determine exhaust air quality to verify filtration efficiency
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HVAC
 Appropriate design, installation, and operation of fume, dust, effluent control
 Wet scrubbers
– Added chemicals for increased adsorption efficiency
 Deep bed scrubbers
– Activated carbon or chemical adsorption granular media
– Specific to type of effluent
– Type and volume prepared
6.2.1 – 6.2.5
HVAC | Slide 31 of 31 May 2006