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1. HVAC | Slide 1 of 29 May 2006
Heating, Ventilation and Air-
Conditioning (HVAC)
Part 2:
HVAC systems and components
Supplementary Training Modules on
Good Manufacturing Practice
Section 7
2. HVAC | Slide 2 of 29 May 2006
Objectives
In the following slides, we will study the components of air-
handling systems in order to:
1. Become familiar with the components
2. Know their functions
3. Become aware of possible problems
HVAC
3. HVAC | Slide 3 of 29 May 2006
HVAC
General
Design of HVAC is dependent on required degree of air
cleanliness
Suitable components should be selected including:
– fans,
– driers,
– filters,
– ducts, grilles, etc.
7.
4. HVAC | Slide 4 of 29 May 2006
+
Production Room
Exhaust air treatment
Central air handling unit
Terminal air treatment
at production room level
Fresh air treatment
(make-up air)
HVAC Main subsystems
5. HVAC | Slide 5 of 29 May 2006
HVAC
Components
Components in HVAC may include, depending on need:
Filters
Fans
– no fan failure; including supply air fans, return air fans,
exhaust air fan, dust extract system fans
Driers
– Drying of air with chemical driers, e.g. rotating desiccant
wheel
Frost coils for preheating air 7.1.1 – 7.1.7
6. HVAC | Slide 6 of 29 May 2006
HVAC
Components
Components in HVAC may include, depending on need:
Snow eliminators
Dust eliminators
Moisture eliminators
Precooling coils
Alarm systems, grilles/diffusers, etc. 7.1.1 – 7.1.7
7. HVAC | Slide 7 of 29 May 2006
FilterSilencer
Terminal filter
Weather louvre Control damper
FanFlow rate controller
Humidifier
Heating
coil
Cooling coil
with droplet
separator
Production Room
Overview components
+
Prefilter
Exhaust Air Grille
Heater
Secondary Filter
Recirculated air
HVAC
8. HVAC | Slide 8 of 29 May 2006
Weather louvre
Silencer
Flow rate controller
Control damper
To prevent insects, leaves, dirt and rain
from entering
To reduce noise caused by air
circulation
Automated adjustment of volume of air
(night and day, pressure control)
Fixed adjustment of volume of air
Components (1)
HVAC
9. HVAC | Slide 9 of 29 May 2006
Heating unit
Cooling unit/
dehumidifier
Humidifier
Filters
Ducts
To heat the air to the proper
temperature
To cool the air to the required
temperature or to remove moisture
from the air
To bring the air to the proper humidity,
if too low
To eliminate particles of predetermined
dimensions and/or microorganisms
To transport the air
Components (2)
HVAC
10. HVAC | Slide 10 of 29 May 2006
Control damper for airflow
De-humidification
Filter Pressure
Gauges
AHU with fan Variable
Speed Controller
Humid room air
Air heater
Regeneration air
Humid room air
Adsorber wheel Dry air
Air-handling unit
HVAC
11. HVAC | Slide 11 of 29 May 2006
Humidifier Silencer Heating and
cooling units
HVAC
12. HVAC | Slide 12 of 29 May 2006
Filter classes Dust filters
Standard Aerosol
FineCoarse ULPAHEPA
10 µ m > Dp > 1 µ mDp > 10 µ m Dp < 1 µ m
F5 - F9G1 - G4 U 14- 17H 11 - 13
EN 1822 StandardEN 779 Standard
HVAC
13. HVAC | Slide 13 of 29 May 2006
Primary panel filter
Secondary filter
HEPA or tertiary filter
HVAC
14. HVAC | Slide 14 of 29 May 2006
Average Efficiency
Integral Value
Peak Arrestance
Local Value
Retention in
%
Penetration Efficiency Penetration
F9 85 0.15
H11 95 0.05
H12 99.5 5x10
-3
97.5 25x10
-3
H13 99.95 5x10
-4
99.75 25x10
-4
U14 99.995 5x10
-5
99.975 25x10
-5
Classification of filters according to their efficiency
HVAC
15. HVAC | Slide 15 of 29 May 2006
Positioning of filters (1)
Filter in terminal positionAHU mounted final filter
Production Room
+
Production Room
HEPA Filter
HEPA Filter
HVAC
16. HVAC | Slide 16 of 29 May 2006
Prefilter
AHU
Main filter
1 2 3
Low level exhausts
Ceiling
exhausts
Positioning of filters (2)
HVAC
17. HVAC | Slide 17 of 29 May 2006
AHU
Prefilter
Final filter
21
Positioning of filters (3)
HVAC
18. HVAC | Slide 18 of 29 May 2006
Swirl Type air diffusors with
terminal filters1 Filter
2 Tightening frame
3 Register outlet
4 Screw fixation for register
1
2
3
4
HVAC
19. HVAC | Slide 19 of 29 May 2006
Low induction
swirl diffusor
(preferred)
High induction
office type diffusor
(avoid)
HVAC
20. HVAC | Slide 20 of 29 May 2006
Regulation of room pressure – pressure differentials concept
Room pressure
gauges
Room pressure indication panel
HVAC
21. HVAC | Slide 21 of 29 May 2006
Flow rate controller
Control damper
Humidifier
Cooling battery
Filters
Ducts
Blocked
Poorly adjusted, bad pressure
differential system
Bad water/steam quality/
poor drainage
No elimination of condensed water/
poor drainage
Incorrect retention rate/damaged/badly
installed
Inappropriate material/internal insulator
leaking
Problems with components
HVAC
22. HVAC | Slide 22 of 29 May 2006
HVAC
In the next slides
Consider different air types, e.g.:
Supply air
Return air (recirculated air)
Fresh air (make-up air)
Exhaust air
And: Concepts of air delivery to production areas:
Recirculation systems
Full fresh-air systems
23. HVAC | Slide 23 of 29 May 2006
+
Production Room
Exhaust
air
Return air
(recirculated)
Fresh air
(make-up air)
Supply
air
Air types
HVAC
24. HVAC | Slide 24 of 29 May 2006
HVAC
Recirculation systems
There should be no risk of contamination and cross-
contamination when air is recirculated
Normally, HEPA filters (EN1822 H13) needed in supply air
stream
– Not required in single product facility with no risk of cross-contamination
– Not required where no dust generation (e.g. secondary packaging)
HEPA filters placed in AHU or terminally
Dust from highly toxic processes should not be recirculated
7.2.1 – 7.2.6
25. HVAC | Slide 25 of 29 May 2006
Ventilation with recirculated air + make-up air
Central Air-Handling Unit
Return air
Exhaust Unit
HVAC
27. HVAC | Slide 27 of 29 May 2006
HVAC
Full fresh-air systems
100% fresh air - normally where toxic products are processed,
and recirculation not recommended
No contamination from fresh air – sufficient filtration needed
Degree of filtration on exhaust dependent on exhaust air
contaminants and environment regulations
Energy-recovery wheels
– Should not be source of contamination
– Relative pressure between supply and exhaust air
7.3.1 – 7.3.3
28. HVAC | Slide 28 of 29 May 2006
Ventilation with 100% fresh air (no air recirculation)
W
Washer (optional)
Central Air-Handling Unit
Production Rooms
Exhaust Unit
HVAC
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Objectives:
For you, as inspectors, to be able to judge whether the air handling systems which you encounter during your factory inspections are adequate or not, it is necessary to know how such systems work, and to be aware of what problems may arise in terms of the components of the system.
Therefore, the objectives of this part of module 3 are to study the components of air handling systems in order to:
Become familiar with the components
Know their functions
Become aware of possible problems
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7. HVAC systems and components
Note: The required degree of air cleanliness in most OSD manufacturing
facilities can normally be achieved without the use of high-effi ciency particulate
air (HEPA) fi lters, provided the air is not recirculated. Many open
product zones of OSD form facilities are capable of meeting ISO 14644-1
Class 8, “at-rest” condition, measured against particle sizes of 0.5 μm and
5 μm, but cleanliness may not be classifi ed as such by manufacturers.
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To understand the air handling systems, it is necessary to know what their components are.
A conventional Air Handling System has 4 sub-systems:
1. Air handling of the incoming (fresh) air: elimination of coarse contaminants and protection from frost if necessary. In the case of air re-circulation, the fresh air is also called make-up air.
2. Central air handling unit (AHU), where the air will be conditioned (heated, cooled, humidified or de-humidified and filtered), and where fresh air and re-circulated air, if any, (indicated here by the dotted line) will be mixed.
3. Air handling in the rooms under consideration (pressure differential system, additional filtration, air distribution).
4. Air exhaust system (filtration).
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7.1 General
7.1.1 There should be no failure of a supply air fan, return air fan, exhaust
air fan or dust extract system fan. Failure can cause a system imbalance,
resulting in a pressure cascade malfunction with a resultant airfl ow reversal.
7.1.2 A schematic diagram of the airfl ow for a typical system serving a
low humidity suite is represented in Fig. 23.
7.1.3 Air should be dried with a chemical drier (e.g. a rotating desiccant
wheel which is continuously regenerated by means of passing hot air
through one segment of the wheel).
7.1.4 The fi gure illustrates the chemical drier handling part of the fresh air/return
air mixture on a by-pass fl ow. The location of the chemical drier should be
considered in the design phase. Examples of appropriate locations include:
— full fl ow of fresh/return air;
— partial handling of fresh/return air (by-pass airfl ow);
— return air only;
— fresh air only; or
— pre-cooled air with any of the above alternatives.
7.1.5 Possible additional components that may be required should be
considered depending on the climatic conditions and locations. These may
include items such as:
— frost coils on fresh air inlets in very cold climates to preheat the air;
— snow eliminators to prevent snow entering air inlets and blocking airfl ow;
— dust eliminators on air inlets in arid and dusty locations;
— moisture eliminators in humid areas with high rainfall; and
— fresh air pre-cooling coils for very hot or humid climates.
7.1.6 Appropriate alarm systems should be in place to alert personnel if a
critical fan fails.
7.1.7 Low-level return or exhaust air grilles are usually preferred. However,
where this is not possible, a higher air change rate may be needed to
achieve a specifi ed clean area classifi cation, e.g. where ceiling return air
grilles are used.
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Another way to look at an air handling system is to consider the different components and to know their function.
Some of the components, particularly the filters, are essential to ensure the quality of the air.
We will later consider individual components in detail.
Of course, a well-designed air handling system must not only be properly designed, but also properly installed, qualified and maintained (sealed ducts, tight filters).
(The trainer should make the audience aware that this slide is just an example, and that all components may not necessarily be present in each system.)
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A typical HVAC unit consists of a small number of elements only.
It is important that these elements are compatible, properly installed, and fulfilling their goal.
Whereas a weather louvre and silencer are less critical elements, the components associated with the flow rate control are essential, as they allow adjustment of the air volumes supplied to the rooms, which in turn forms the base for a pressure differential concept: to have an automated or a fixed system is largely a financial matter, but a fixed system is more difficult to set up.
Silencer – check internal lining material of silencer as this can cause contamination.
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Heating and cooling units (batteries), as well as humidifiers are used to adjust the climate in the room (temperature and humidity).
Special de-humidifiers, on a dessiccant base, will be addressed later.
Filters are one of the main components, as they determine the size of airborne particles that pass through them, and thus the hygiene class.
It is wise to protect the finer filters by pre-filters, thus extending their life cycles, and making them less prone to clogging.
Ducts transport the air from the air handling units to and from the rooms. Inspectors must verify that ducts do not have internal insulation as this is a great source of contamination.
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Dampers to control pressure differentials are important. They can be automated or fixed. As filters get dirty the system pressure losses increase, and if airflow is not regulated, the flow decreases and pressure differentials change. This could cause flow reversal and cross-contamination. Variable speed drives for fan motors are also commonly used to control airflow.
In some cases, it is necessary to have very dry air for galenical reasons in certain rooms (production of effervescent tablets and humidity sensitive products in general).
To generate dry air, the air supplied to the production is passed over an adsorbant (silicagel, lithium chloride, etc.) where the humidity is removed from the air.
The adsorbant is then re-generated, on a continuous or on a batch-wise base.
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This slide shows additional elements of the air handling units.
For humidification purposes, especially in clean areas, high purity water should be used, to avoid contamination.
The silencer is not important from a GMP point of view, but from an environmental one, as ventilation units can be very noisy. Be sure that the silencers are manufactured of suitable materials as the linings of standard silencers can contaminate air with particulates.
Depending on the local legislation, the installation of silencers can be mandatory.
The cooling unit is important during the hot season. Be aware that stagnating water (condensed water) can bring bacterial growth, which can contaminate the filters, pass through them (depending on their retention properties) and end up contaminating production areas.
It is essential that there is no stagnating water. Cooling coils can be sanitized as well.
Do remember that, if filters are not properly maintained, micro-organisms may grow through the filters and be carried towards the production rooms.
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The filtration efficacy depends on several mechanisms, and results in a rough filter classification.
The diagram shows the commonly used classification, with current abbreviations G = Gross, F= Fine, H= High, U= Ultra.
Filters are certified by the suppliers (challenge/efficiency test), but are often not properly installed or can be damaged. Leak tests (integrity tests), showing leakage of air through the filter itself or through its frame, therefore, have to be performed. Integrity tests are usually only carried out on the Aerosol filters (HEPA & ULPA).
Integrity or penetration testing is performed to detect leaks from the filter media, filter frame and seal. The challenge is a poly-dispersed aerosol usually composed of particles ranging in size from one to three microns. The test is done in place and the filter face is scanned with a photometer probe; the measured downstream leakage is taken as a percentage of the upstream challenge. Integrity tests should be carried out with filters installed in the system and should be carried out by an independent body (not the filter supplier).
The efficiency test, on the other hand, is used to determine the filter&apos;s rating. This test uses a mono-dispersed aerosol of 0.3 micron size particles, relates to filter media, and usually requires specialized equipment. Downstream readings represent an average over the entire filter surface. Therefore, leaks in a filter may not be detected by an efficiency test.
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This slide shows
Primary Panel filters, which are used mainly for lower filtration efficiency or as pre-filters
Secondary filters, consisting of mini-pleated media or filter bags, and is used for higher filtration efficiency.
HEPA or tertiary filters, usually being the final filter in the system, providing the highest filtration efficiency.
Though there is a strong relationship between filter efficiency and cleanroom class, a filter of a high efficiency does not guarantee a high cleanroom class, as many other elements play a role, such as
Air flow (how the air is extracted, how well the room is “flushed”)
Air speed and number of air changes
Positions of air terminals
Layout and presence of objects
Personnel and clothing
Equipment (not all machines are designed to operate in a clean environment!)
Proper installation and proper maintenance
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This table gives an idea of the efficiency of the filters, calculated across the entire surface (integral value) or in particular spots (local value).
Referring to filter ratings by percent efficiency is misleading, as there are so many different types of tests that give different efficiencies for the same filter. This can be very confusing and it is better to refer to the Committee of European Normalisation (EN) test rating i.e. G4, F8, H12, etc.
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In some of the previous slides, we have seen filters both in the central air handling units ( AHU ) and terminally mounted at the production rooms.
The filtered air entering a production room can be coming from:
an air-handling unit, equipped with pre-filtration and the main (HEPA) filter, but at some distance from that room (left drawing);
an air-handling unit, equipped with pre-filtration in the AHU, and an additional filter (HEPA) situated immediately on the air outlet (right drawing).
In many cases, there are only filters in the AHU. However, for injectables and sterile forms, it is recommended that they be placed in terminal position, though there is a growing tendency to have terminal filters in all rooms where open products are handled. It is recommended that classes A & B (ISO 4, 5 & 6) have terminal HEPA filters. (Refer to: WHO Export Committee on Specifications for Pharmaceutical Preparations. Thirty-second Report. Geneva, World Health Organization, 1992:59-60 (Technical Report Series, No. 823). Annex 1, 17.3.)
If we look at the advantages and disadvantages of terminal or non-terminal filters, we can say that generally speaking, the terminal positioning
is more expensive;
provides a better protection (any problem arising from the ducts is eliminated);
is the preferred method in cleanroom classes with high requirements.
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Filters can be in different positions, when one considers the central AHU and the rooms.
This slide shows an HVAC installation feeding 3 rooms, each one with terminal filters, all filters protected by a remote pre-filter.
Room 1 has a turbulent air flow, with low level exhaust.
Room 2 has a uni-directional (laminar) air flow over the largest part of the surface, hence the large number of filters.
Room 3 has a turbulent air flow, with ceiling exhaust.
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This slide shows an HVAC installation feeding two rooms, each one without terminal filters, but with remote final filters protected by a pre-filter.
Room 1 has a turbulentair flow, with low level exhaust.
Room 2 has a turbulent air flow, with ceiling exhaust.
If there is no filter in terminal position, it should be ascertained that there are no elements between the main filter and the air outlets which could add contamination. No elements such as fans, heating/cooling batteries, should be situated downstream of the final filter.
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The air flows into the rooms via so-called registers (diffusors), which are built and installed in such a way that the air is distributed evenly.
Machinery or furniture can block the passage of air from the register to the exhaust point, creating unflushed zones, where counts of particles and micro-organisms could be higher.
It is therefore important to consider the content of a clean room, when planning the HVAC system.
In many cases, the terminal filter panel and diffusors are incorporated into one unit.
It is also important that the air diffuser supplies air evenly and does not induce the circulation of dust in the room – as illustrated by the next slide.
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The diffuser on the left is a normal office type diffuser which induces a lot of air to rise vertically from the floor towards the ceiling. The rising induced air has the potential for carrying a lot of dust upwards which is then spread throughout the room with the air supply. This type of diffuser readily spreads contaminants in the room and should be avoided.
The preferred type of diffuser for cleanroom applications is the swirl diffuser, or perforated plate diffuser. These types do not promote the spread of dust within the room.
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One of the main points in the design of production rooms is the pressure differentials concept.
Pressure differentials must be defined, monitored and alarmed in critical cases.
The overpressure of each room is measured against a reference point in the factory (point zero). As discussed earlier, the pressure regulation can be fixed or automated. Pressure control can be by means of automatic air flow control dampers (as shown in slide 15) or by means of fan speed control. Whatever the means used it is important to ask the manufacturer how they ensure that the pressure cascade is maintained as the filters get dirty.
In the following slides, we are going to see that an overpressure concept can be very different for sterile products and for solid products.
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Problems may arise with components, with the following consequences:
Flow rate controllerBlockedNo control of pressure differentials
Control damperPoorly adjustedBad pressure differential systems
HumidifierBad water/Risks of microbial contamination
steam quality
Cooling UnitNo eliminationRisks of microbial contamination
of condensed water
FiltersIncorrect retention Risks of contamination
rate(particles, micro-organisms)
DamagedFilter integrity fails
Badly installedRisks of contamination (particles, micro-organisms)
DuctsInappropriate materialDanger of corrosion
Leaking duct workIntake of unfiltered air
Internal insulationInability to properly clean
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In this session we want you to achieve the following:
1. To understand the key issues in relation to quality assurance and quality control.
2. To understand the special needs in terms of organization, procedures, processes and resources, including staffing.
3. In your group session, to look at the special situations and problems that you face in these areas in your country, and to develop practical solutions.
This area of work is potentially difficult because of the need to understand clearly the difference between quality management, quality assurance (QA) and quality control (QC).
We will be looking at the issues that can arise in implementation, and at your own experiences.
We will consider questions such as what to do about the owner of a factory who insists on appointing his/her son or daughter, who is not qualified, into a position of responsibility, and what to do about a factory that insists that it can manufacture penicillin products without cross-contamination risk, in the same equipment and premises used for manufacture of other types of product.
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There are different air types to be considered within the air handling system:
Fresh air (if the plant is of the re-circulation type, it is necessary to replace some of the re-circulating air with fresh air, which is then called make-up air).
A proportion of about 15% fresh air is normal, but this proportion can vary, depending on factors such as number of people, National Regulatory Authority requirements, the presence of certain substances in the air, leakage due to pressure control, etc.
Supply air to the rooms
Exhaust air from the rooms
Return air (about 85% is being re-circulated)
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7.2 Recirculation system
7.2.1 There should be no risk of contamination or cross-contamination
(including by fumes and volatiles) due to recirculation of air.
7.2.2 Depending on the airborne contaminants in the return-air system
it may be acceptable to use recirculated air, provided that HEPA fi lters are
installed in the supply air stream to remove contaminants and thus prevent
cross-contamination. The HEPA fi lters for this application should have an
EN1822 classifi cation of H13.
7.2.3 HEPA fi lters may not be required where the air-handling system is
serving a single product facility and there is evidence that cross-contamination
would not be possible.
7.2.4 Recirculation of air from areas where pharmaceutical dust is not generated
such as secondary packing, may not require HEPA fi lters in the system.
7.2.5 HEPA fi lters may be located in the air-handling unit or placed terminally.
7.2.6 Air containing dust from highly toxic processes should never be
recirculated to the HVAC system.
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This slide illustrates a typical re-circulated air setup, where a central unit distributes a mixture of fresh and re-circulated air to different production rooms.
A part of the exhaust air is collected in a central duct, treated (filtered) and exhausted. The rest is re-circulated (dotted line).
With control dampers, the proportions of fresh and re-circulated air can be adjusted.
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7.3 Full fresh air systems
Fig. 26 indicates a system operating on 100% fresh air and would normally
be used in a facility dealing with toxic products, where recirculation of air
with contaminants should be avoided.
7.3.1 The required degree of fi ltration of the exhaust air depends on the
exhaust air contaminants and local environmental regulations.
7.3.2 Energy-recovery wheels should normally not be used in multiproduct
facilities. When such wheels are used they should not become a
source of possible contamination (see Fig. 27). Note: Alternatives to the
energy-recovery wheels, such as crossover plate heat exchangers and watercoil
heat exchangers, may be used in multiproduct facilities.
7.3.3 The potential for air leakage between the supply air and exhaust air
as it passes through the wheel should be prevented. The relative pressures
between supply and exhaust air systems should be such that the exhaust air
system operates at a lower pressure than the supply system.
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This slide illustrates a typical 100% fresh air setup, where a central unit distributes the fresh, treated air to different production rooms.
The exhaust air is collected in a central duct, treated (filtered or washed) and eliminated. The degree of exhaust air filtration will depend on contaminants in the exhaust air and also on environmental regulations.