hvac | slide 1 of 47 2013 heating, ventilation and air- conditioning (hvac) part 2: air flows,...

HVAC | Slide 1 of 47 2013

Heating, Ventilation and Air-

Conditioning (HVAC)

Part 2: Air flows,

Pressure concepts

Good Manufacturing Practices: HVAC

WHO Technical Report Series, No. 961, 2011. Annex 5


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Objectives

To continue from previous section of Part 1, now focus on:

Air filtration and air flow patterns

The role of HVAC in dust control

HVAC system design and its components (part 3)

Commissioning, qualification and maintenance (part 4)


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Air Filtration

Degree of filtration of air is important to prevent contamination

Type of filters to be used is dependent on:– Quality of ambient air, – Return air / re-circulation– Air change rates– National requirements– Products and required class of clean room etc.

Manufacturer to determine, select and install appropriate filters for use 4.2.1, 4.3.3


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Levels of protection and recommended filtration

4.2.1 - 2

Level of protection

Recommended filtration

Level 1Primary filters, e.g. EN779 G4

Level 2 Production area with 100% outside air: Primary plus secondary filter (e.g. EN779 G4 plus F8 or F9 filters)

Level 3Production facility operating on re-circulated plus ambient air, where potential for cross-contamination exists: Primary plus secondary plus tertiary filters (e.g. EN779 G4 plus F8 plus EN1822 H13 filters) (For full fresh air system, without recirculation, G4 and F8 or F9 filters are acceptable)


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Contamination can be prevented by considering: Appropriate materials of construction of HVAC components

Placement of components (e.g. upstream of final filters)

Design and appropriate access (from outside) to dampers, filters and other components

Personnel operations and protection

Airflow direction

Air distribution component design, installation and location

Diffusers (type, design, location)

Air supply and air exhaust location4.2.4 – 4.2.10


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Induction diffuserInduction diffuser


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Perforated platePerforated plate


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Swirl type diffuserSwirl type diffuser


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Airflow patterns

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.


Unidirectional/laminar

displacement of dirty air

Turbulent

dilution of dirty air

Airflow patterns

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PrefilterAirflow patterns

AHU

Main filter

Unidirectional TurbulentTurbulent

1 2 3

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Unidirectional airflow (UDAF)

Often used in weighing and sampling areas (Airflow Protection Booths) and provides:

Dust containment and product and operator protection

Note: For Airflow Protection Booths (APB):

Airflow velocity should not affect balance (may be lower than for Class A areas)

Position of material, balance, operator determined and validated – no obstruction of airflow or risk 4.3


Workbench (vertical) Cabin/booth Ceiling

Airflow patterns

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Unidirectional airflow (UDAF): Sampling and weighing area classification – same as other

processing areas following sampling and dispensing

Dust containment shown through smoke tests as part of validation / qualification

Location and type of return and exhaust grilles

Cleaning and maintenance

Will discuss examples in the following figures

4.3.


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Infiltration

Prevent infiltration of unfiltered, contaminated air from outside

Facilities normally under positive pressure to the outside

Building structure well sealed

Some cases - negative pressure (e.g. penicillin manufacture). Special precautions to be taken. See separate guidelines

4.4.1 – 4.4.4


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Cross-contamination

Multiproduct facility – even if in different areas - risk for cross contamination (dust from area to area)

Correct direction of air movement and pressure cascade

Normally, corridors positive to cubicles and cubicles positive to atmosphere

Consider building structure, ceilings, walls, doors etc

Different concepts discussed in following slides4.5


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Displacement concept

Not a preferred method (Found in older facilities)

Based on low pressure differentials and high airflows

Air supplied to the corridor – then through the doors (grilles) to the cubicles

Air extracted at the back of the cubicle

Velocity high enough to prevent turbulence in doorway4.6


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Pressure differential concept

Used where there is low dust in areas. Alone or in combination with other control techniques

High pressure differential, low airflow, and airlocks

Airlock types include: Cascade, sink and bubble type (See next slides)

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

4.7


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Essential / critical parameter here is pressure differentials

Risk assessment may be done

High enough to achieve containment; low permissible when airlocks are used

No flow reversal should take place – therefore appropriate limits e.g. 5Pa to 20 Pa

No turbulence

No overlap (two adjacent rooms)

4.7


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Adequate room pressure differential indication provided

Each critical room pressure must be traced back to ambient pressure (by summation of the room pressure differentials) – provides actual absolute pressure

Gauges with appropriate range and graduation scale to enable accurate reading; analogue or digital; as pressure differentials or absolute pressures

Normal operating range, alert and action limits defined and displayed

OOS condition should be easily identifiable4.7


N o te : D ire c t io n o f d o o r o p e n in g re la t iv e t o ro o m p re s s u re 1 5 P a1 5 P a1 5 P aE3 0 P a Pa s s a g e 0 P aA irLo ck R o o m 3 R o o m 2 R o o m 11 5 P a A ir Lo ckA ir Lo ck

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Calibrated and qualified monitoring devices, verified at intervals

Linked to alarm system

Monitoring and recording of results

Doors open to higher pressure, self closers

Doors interlocked where possible

4.7


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Dust extraction system design is important as it may impact on pressure cascade

Central systems interlocked with AHUs

No airflow between rooms through common system

What happens in the case of component failure?

4.7


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Airlocks and Material Pass-though-hatches (PTH)

Can be used to separate two zones

Dynamic and passive PTH

Also designed as bubble, sink or cascade

See next slides for design principles 4.7


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What type of airlock is this?

How does it work?

Any examples of whereIt can be used?


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Physical barrier concept

In some cases, impervious barriers are used to prevent cross-contamination

Closed systems

Pump or vacuum transfer

4.8


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Temperature and relative humidity (RH)

Consider materials and product requirements as well as operator comfort in the design of the HVAC

Where conditions are required, provide for control, monitoring and recording

Alert and action limits; minimum and maximum limits

Premises appropriately designed

HVAC design to achieve and maintain conditions in different seasons

4.9


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Relative humidity (RH)

Low RH areas need well sealed walls and ceilings, and preferably air locks

Remove or add moisture as necessary

Dehumidification– Refrigerated dehumidifiers - cooling media– Chemical dehumidifiers

Humidifiers should not be sources of contamination

– Use of pure steam or clean steam

– No chemicals that can have a detrimental effect

4.9


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Relative humidity (RH)

Humidifiers should be well drained - 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

4.9


Dust Control Where possible - 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 in extraction system to prevent dust settling in ducting

– Calculations and measurements

Periodic checks for build up

Risk analysis – airflow direction

5.1. – 5.6

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Dust Control (2)

Normally air supplied through ceiling diffusers, near the door

Air extracted from low level (rear)

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.

5.7. – 5.8.


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Dust collection system

Exhaust air dust

Exhaust air from equipment and some areas of production can carry heavy loads of dust, vapours and fumes (e.g. FBD, coating, weighing)

Filtration may be needed to protect environment (see National legislation)

Location of the inlet and exhaust points relative to one other important to prevent contaminants taken into inlet air

6.1.1 – 6.1.2


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Exhaust air dust

Wet scrubbers can also be used

Contaminated air is collected

Dust is treated with a mist/spray / water

Clean air is exhausted

hvac | slide 1 of 47 2013 heating, ventilation and air- conditioning (hvac) part 2: air flows,...

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