Review of Design Methods to control Internal Environment in clean rooms

1. 4
By
Review of Design Methods to Control
Internal Environment in Cleanrooms
Professor Moustafa M. Elsayed
Consultant, EGEC
moustafa.elsayed@egec-xprt.com

2. 1
4
By
Review of Design Methods to Control
Internal Environment in Cleanrooms
Professor Moustafa M. Elsayed
Consultant, EGEC
moustafa.elsayed@egec-xprt.com
5
Outline
Introduction
Standards & Classifications
Contamination
Testing
Types of Clean Areas
HVAC System Design
Air Flow Pattern
Air Filtration
Design Parameters
Air Distribution
T & RH Control
Pressurization Control
Validation Tests
HVAC System Cost
Other Design Consideration
Anterooms
6
Introduction
Definition of a cleanroom.
First use of cleanrooms: NASA (so-called white room).
Objectives of cleanrooms operation are:
To maximize productivity
To reduce rejection
To achieve unbiased experimentation
To prevent contamination
To increase product shelf life 7
Table 1 Typical Cleanroom Applications for Various
Segments of Users
ApplicationsUserGroup
Wafer Fabrication, Microprocessor, Large Wafer
Sizes, IC, Hybrids, Flat Panel Displays
SemiconductorsA
Computer, Compact Disc, Printed Circuits, Disk
Drivers, Other Magnetic Media, Sensor/Relays,
Computer Peripherals
ElectronicsB
Liquid Drug Filling, Biological Research, Botanical,
Pharmaceutical Preparations, Biomedical,
Biotechnology
PharmaceuticalC
Relative Share of Cleanrooms Users

3. 2
8
ApplicationsUserGroup
Defense Contractors, Satellites, Space Craft Inst.,
Aircraft Instruments
AerospaceD
Aseptic food Process, Beverage Filling, Cereal
Manufacturing, Dairy Pasteurization, Food
Preparation, Agriculture
FoodE
Surgical Transplants, Artificial Limb Prod., Surgical
Suites, I.V. Drug Injections, Blood Banks
Medical
F
Automotive, Laser/Optics, Superconductor,
Rubber/Plastics, Photography, Holography,
Chemicals, Glasses
OthersG
Relative Share of Cleanrooms Users
9
Relative Share of Cleanrooms Users
A B C D E F G
Users
Fig. 1 Relative Share of Cleanrooms Users (See Table 1)
10
Outline
Introduction
Standards & Classifications
Contamination
Testing
Types of Clean Areas
HVAC System Design
Air Flow Pattern
Air Filtration
Design Parameters
Air Distribution
T & RH Control
Pressurization Control
Validation Tests
HVAC System Cost
Other Design Consideration
Anterooms
11
Cleanroom Standards and
Classifications
The most widely accepted standards of cleanroom are:
ISO EN 14611-1 1999
US Federal Std 209E 1992
German VDI 2083 1990
EEC cGMP 1989
France AFNOR 1989
British BS 5295 1989
Japan JIS B 9920 1989

4. 3
12
Cleanroom Standards and
Classifications
Table 2 Air Classifications for Internal Cleanroom Standards
(New WayZ, 2003)
Approx.
Particles
Per m3
0.5mµµµµ
ISO
EN 14644-1
1999
US
209E
1992
US
209E
Imperial
Germany
VDI
2083
1989
EEC
CGMP
1989
France
AFNOR
1989
Britain
BS 5295
1989
Japan
JIS B
9920
1989
1
3.5 2 0 2
10 M 1
35 3 M 1.5 1 1 C 3
100 M 2
353 4 M 2.5 10 2 D 4
1000 M 3
≥
13
Approx.
Particles
Per m3
0.5mµµµµ
ISO
EN 14644-1
1999
US
209E
1992
US
209E
Imperial
Germany
VDI
2083
1989
EEC
CGMP
1989
France
AFNOR
1989
Britain
BS 5295
1989
Japan
JIS B
9920
1989
3530 5 M 3.5 100 3 A+B 4000 E or F 5
10000 M 4
35300 6 M 4.5 1000 4 G or H 6
100000 M 5
353000 7 M 5.5 10000 5 C 400000 J 7
1000000 M 6
3530000 8 M 6.5 100000 6 D 4000000 K 8
10000000 M 7
100000000 9 M 7.5 1000000 40000000 L 9
Cleanroom Standards and
Classifications
≥
14
Cleanroom Standards and
Classifications
Table 3 Federal Standard 209D classification of cleanrooms
100,00010,0001000100101
Federal Standard 209
classification
100,00010,0001000100101No. of particles/ft3, m0.5 µ≥
15
The ISO standard has 9
classes for clean air: classes 1
to 9.
The ISO class: is related
particles of size 0.1 mµ or
larger.
Concentration limit Cn
The ISO standard
08.21.0 )(10
D
N
nC =

5. 4
16
The ISO standard
Table 4 Airborne Particulate Cleanliness Classes
(by cubic meter) as per ISO 14644-1
CLASS
Number of Particles per Cubic Meter by Micrometer Size
0.1 µµµµm 0.2 µµµµm 0.3 µµµµm 0.5 µµµµm 1 µµµµm 5 µµµµm
ISO 1 10 2
ISO 2 100 24 10 4
ISO 3 1,000 237 102 35 8
17
The ISO standard
Number of Particles per Cubic Meter by Micrometer Size
CLASS
5 µµµµm1 µµµµm0.5 µµµµm0.3 µµµµm0.2 µµµµm0.1 µµµµm
833521,0202,37010,000ISO 4
298323,52010,20023,700100,000ISO 5
2938,32035,200102,000237,0001,000,000ISO 6
2,93083,200352,000ISO 7
29,300832,0003,520,000ISO 8
293,0008,320,00035,200,000ISO 9
18
Table 5 Applications of ISO Class 1 to 8
Application
US
209E
ISO
Class
Latest wafer and chip manufacturing, Hard disk manufacturingISO 1
Semi-conductor manufacturing, Pharmaceutical productsISO 2
Compact disk manufacturing, Optical manufacturing,
Integrated circuits manufacturing
1ISO 3
High speed video duplication, Glass lamination, semi-
conductors manufacturing
10ISO 4
Applications of bacteria-free or particulate free environment
like manufacturing of aseptically-produced injectable
medicines. Immuno-suppressed patients (e.g. after bone
marrow transplant operations)
100ISO 5
19
Application
US
209E
ISO
Class
Manufacture of high quality optical equipment. Assembly and
testing of precision gyroscopes. Assembly of miniaturised
bearings.
1000ISO 6
Assembly of precision hydraulic or pneumatic equipment,
servo-control valves, precision timing devices, high grade
gearing.
10,000ISO 7
General optical work, assembly of electronic components,
hydraulic and pneumatic assembly.
100,000ISO 8
Table 5 Applications of ISO Class 1 to 8

6. 5
20
Outline
Introduction
Standards & Classifications
Contamination
Testing
Types of Clean Areas
HVAC System Design
Air Flow Pattern
Air Filtration
Design Parameters
Air Distribution
T & RH Control
Pressurization Control
Validation Tests
HVAC System Cost
Other Design Consideration
Anterooms
21
Airborne Contaminants in
Cleanrooms
Internal sources: people (finger
prints, skin oil, hand cream, face
cream, polish, face powder, body
oil and grease, skin, scales, hair,
clothing lint, sneezing, coughing,
etc.).
Internal sources: process equipment
and manufacturing process
(emission of gases, oil, grease, oil
vapors, and particle shedding
materials).
External sources: infiltration to
cleanroom.
22
Airborne Contaminants in
Cleanroom
Table 6 Particle Size Distributions from Human Sneeze or
Cough
CoughSneeze
Diameter in
micrometer
66,000800,000< 1
21,000686,0001 - 2
1,600280,0002 - 4
1,290134,0004 - 8
49036,0008 - 16
854,50022
90,7651,940,000Total 23
Outline
Introduction
Standards & Classifications
Contamination
Testing
Types of Clean Areas
HVAC System Design
Air Flow Pattern
Air Filtration
Design Parameters
Air Distribution
T & RH Control
Pressurization Control
Validation Tests
HVAC System Cost
Other Design Consideration
Anterooms

7. 6
24
Testing of Air Classification
Sampling the environment using a
proprietary automatic air sampler is
the most common method.
Standards for cleanroom monitoring
require assessment of number of
particles over a range of at least 2
sizes.
Normally it is common to use
0.5µm and 5µm as the range
reported.
25
There are possible three states to exist in a clean
space:
Testing of Air Classification
1. Clean space commissioned but without equipment
installed.
2. Clean space completely fitted out and operational,
without personnel movement.
3. Clean space fully operational under normal or worst case
conditions.
26
Testing of Air Classification
Table 7 Required Testing as per ISO 14644-2
Schedule of Tests to Demonstrate Continuing Compliance
Test Parameter Class
Maximum
Time Interval
Test Procedure
Particle Count Test
<= ISO 5 6 Months
ISO 14644-1 Annex A
> ISO 5 12 Months
Air Pressure Difference All Classes 12 Months ISO 14644-1 Annex B5
Airflow All Classes 12 Months ISO 14644-1 Annex B4
27
Testing of Air Classification
Table 8 Optional Testing as per ISO 14644-2
Schedule of Additional Optional Tests
Test ParameterClassMaximum
Time Interval
Test Procedure
Installed Filter LeakageAll Classes24 MonthsISO 14644-3 Annex B6
Containment LeakageAll Classes24 MonthsISO 14644-3 Annex B4
Airflow VisualizationAll Classes24 MonthsISO 14644-3 Annex B7

8. 7
28
Outline
Introduction
Standards & Classifications
Contamination
Testing
Types of Clean Areas
HVAC System Design
Air Flow Pattern
Air Filtration
Design Parameters
Air Distribution
T & RH Control
Pressurization Control
Validation Tests
HVAC System Cost
Other Design Consideration
Anterooms
29
Types of Clean Areas
Conventional Clean Area.
Unidirectional flow Clean Area.
Mixed flow Clean Area.
Isolators or Microenvironment Clean Area.
30
Conventional Clean Area
Turbulently-ventilated or
non-unidirectional flow.
Area is distinguished by
their method of air supply.
Air supply diffusers or
filters in the ceiling.
Return air from grills in
ceiling, low-side wall, or the
floor.
31
Unidirectional flow Clean Area
Widely known as clean area
with laminar flow, which is
terminologically wrong.
Supply: bank of high
efficiency filters (HEPA).
Return/ exhaust air is from
low-side wall or floor.

9. 8
32
Mixed flow Clean Area
Cleanroom is
conventionally
ventilated but where the
product is exposed to
contamination, a
unidirectional flow
cabinet or workstation
is used.
33
Isolators or Microenvironment
Clean Area
Fig 5 Isolator used to protect the critical production area
These are used within a cleanroom.
34
Contaminated Rooms
Manufacturing processes:
toxic chemicals or
dangerous bacteria.
Examples: pharmaceutical
industry and biotechnology
industry.
Design of contaminated
rooms: similar to that used
in cleanrooms.
35
Outline
Introduction
Standards & Classifications
Contamination
Testing
Types of Clean Areas
HVAC System Design
Air Flow Pattern
Air Filtration
Design Parameters
Air Distribution
T & RH Control
Pressurization Control
Validation Tests
HVAC System Cost
Other Design Consideration
Anterooms

10. 9
36
HVAC System Design
Cleanrooms HVAC system design: clean class.
Control the internal environment of cleanroom.
Function:
Cleanliness level
Room temperature and
relative humidity
37
Room clean class: controlling both external and
internal source of contaminants.
Controlling external source:
HVAC System Design
Filtration of all outdoor air to the room.
Keeping room at higher pressure than surroundings.
Sealing of opening in room where penetration of
ducts or pipe may exist.
Controlling the internal sources:
Proper gowning procedure.
Proper cleanroom garments.
Proper airflow pattern and quantity.
38
Requirement of HVAC System
Airflow rate to the room (ACH)
Airflow distribution in the room
Airflow pattern.
Location of air supply
outlet and air return grills.
Clean air velocity entering
the room.
Return air face velocity at
return air grill.
39
Type of air filter and its
efficiency.
Control system to maintain
room pressure and temperature
and/ or relative humidity.
Supply air temperature and/ or
humidity to the room (if
applied).
Requirement of HVAC System

11. 10
40
Table 9 Recommendation of HVAC Design Parameters for
Various Cleanroom Classes
ISO ISO 3 ISO 4 ISO 5 ISO 6 ISO 7 ISO 8 Ref
FS 209 1 10 100 1,000 10,000 100,000
ACH (Note 1) 540-600+ 540-600 400-480 120-150 45-60 20-30 1
360-540 300-540 240-480 150-240 60-90 5-48 2, 6
500-600 500-600 500 40-120 20-40 10-20 3
600 250-600 150-250 50-120 20-50 4
250-700 5
450-640 420-600 300-480 180-300 36-90 6
41
ISO ISO 3 ISO 4 ISO 5 ISO 6 ISO 7 ISO 8 Ref
FS 209 1 10 100 1,000 10,000 100,000
Ceiling
coverage
98% 85-90% 60-80 40-50% 10-20% 5% 1
100% 100% 100% 25-40% 20% 10% 2
90-100% 90-100% 90% 20-50% 10-20% 5-10% 3
100% 70-100% 30-60% 10-30% 5-10% 4
100% 100% 75% 40% 30% 15% 6
Table 9 Recommendation of HVAC Design Parameters for
Various Cleanroom Classes
42
ISO ISO 3 ISO 4 ISO 5 ISO 6 ISO 7 ISO 8 Ref
Filter Type ULPA
HEPA
ULPA
HEPA
ULPA
HEPA HEPA HEPA
1, 2,
6
Filter
efficiency, %
99.9995
@ .12
micron
99.999
@ 0.3
micron
99.99 99.99 99.97 95.00 1
99.9995
@ .12
micron
99.99
@ 0.3
micron
99.99
@ 0.3
micron
99.99
@ 0.3
micron
99.99
@ 0.3
micron
2
99.99995
@ .12
99.99995
@ .12
99.99995
@ .12
99.99995
@ .12
99.99
@ .3 to .5
micron
99.99
@ .3 to .5
micron
6
Table 9 Recommendation of HVAC Design Parameters for
Various Cleanroom Classes
43
ISO ISO 3 ISO 4 ISO 5 ISO 6 ISO 7 ISO 8 Ref
Raise floor
return
must must best best
1,2
Low wall
return
Note 2 common common common 1,2
common common common common common 4
Ceiling return common common 1,2
common 4
Max
horizontal
distance to
return, m
3 6 9
Unidirectional
flow
Must Must Must 2, 6

12. 11
44
ISO ISO 3 ISO 4 ISO 5 ISO 6 ISO 7 ISO 8 Ref
Inlet clean air
velocity, m/s.
See Note 3
0.305-.457 0.005-0.041 0.203-.406 0.127-.203 0.051-076 0.005-.041 2
0.45 0.45 0.45 0.15 -0.45 0.15 - 0.45 0.15- .0.45 3
0.36- 0.56 0.36- 0.56 0.36- 0.56 0.36- 0.56 0.36- 0.56 0.36- 0.56 4
0.38-0.46 0.36-0.41 0.26-0.36 0.15-0.25 0.10-0.15 0.08-0.1 6
Return air
face velocity,
m/s.
0.5 - 1 1 – 2.5 2.5 3
Table 9 Recommendation of HVAC Design Parameters for
Various Cleanroom Classes
45
Note 1: Upper limit of ACH my be increased as required by heat load
Note 2: Possible only when wall distance from room center does not exceed 12 ft (3.6 m)
Note 3: Clean air velocity is taken as the terminal outlet air velocity to space
Ref 1: www.modularcleanrooms.com
Ref 2: Engineering Manual (2000)
Ref 3: Communication and visit to several cleanrooms existing facilities
Ref 4: National Partitions and Interior, Inc (1998)
Ref 5: Rumsey (2003)
Ref 6: Jaisinghani (2003)
Ref 7: Pavlotsky (2004)
Table 9 Recommendation of HVAC Design Parameters for
Various Cleanroom Classes
46
Outline
Introduction
Standards & Classifications
Contamination
Testing
Types of Clean Areas
HVAC System Design
Air Flow Pattern
Air Filtration
Design Parameters
Air Distribution
T & RH Control
Pressurization Control
Validation Tests
HVAC System Cost
Other Design Consideration
Anterooms
47
Air Flow Pattern
Factors for selection of
airflow pattern:
Clean class of the room
Equipment layout
Available space for
environmental control
equipment (AHU,
HEPA filter, etc.)
Available investment.
Types: unidirectional and the
non-unidirectional air flow
patterns.
Unidirectional airflow
pattern: parallel streamlines.
Non-unidirectional flow:
airflow is not in parallel
streamlines.

13. 12
48
Fig. 7 Schematic of unidirectional airflow pattern in a cleanroom with
return air at low-wall level
Unidirectional airflow
49
Unidirectional airflow: ISO 5 or better.
Unidirectional airflow: Vertical or horizontal air flow.
Vertical flow:
Clean air from the ceiling and air return through the
floor or low-level sidewall.
Advantage that it washes internal generated particles
in the outlet direction from the room.
Unidirectional airflow
50
Horizontal flow:
Clean air from one wall and returned through the opposite
wall.
Disadvantage: contaminating particles to another location
where cleanliness level is very critical to maintain.
For this reason horizontal unidirectional air flow pattern is
limited in its application.
Unidirectional airflow
51
Fig. 8 Schematic of non-unidirectional airflow pattern in a cleanroom with
return air at low-wall level
Non-unidirectional airflow

14. 13
52
Non-unidirectional airflow
Non-unidirectional airflow: clean air from some parts in
ceiling and returning the air from floor, low-level
sidewall, or from some parts in the ceiling.
Flow: non-parallel streams.
Rooms are cleaned by dilution effect.
This type of flow is not recommended for clean class
level of ISO 5 or better.
53
Unidirectional Workstations
Unidirectional airflow pattern: clean classes of ISO 5 or
better (High ACH).
Energy saving: unidirectional workstations are usually
recommended for the manufacturing process.
54Fig. 9 Unidirectional Vertical Flow Workstation
Unidirectional Workstations
55
Unidirectional Workstations
Fig. 10 Unidirectional Horizontal Flow Workstation

15. 14
56
Outline
Introduction
Standards & Classifications
Contamination
Testing
Types of Clean Areas
HVAC System Design
Air Flow Pattern
Air Filtration
Design Parameters
Air Distribution
T & RH Control
Pressurization Control
Validation Tests
HVAC System Cost
Other Design Consideration
Anterooms
57
Function: control of particulates and airborne
microorganisms from external and internal
sources.
Design Factors:
Resistance to airflow
through the filter
Clean class
Air Filtration
58
• Types of Filters: HEPA &
ULPA
• Filter efficiency:
Arrestance
Dust-Spot Efficiency
Particle Size
Efficiency.
Fractional Efficiency
or Penetration: DOP
efficiency
Air Filtration
59
Expression for a fractional efficiency:
inoutinf CCC /)( −=η
Standard efficiencies:
HEPA filters: 99.95%, 99.97% and 99.99 @ 0.3 mm
size particle.
ULPA air filters: 99.9995% @ 0.12 mm size particle
Supper ultra ULPA air filter: 99.999999% @ 0.12
mm size particle.
Air Filtration

16. 15
60
Recommended air face velocity: 90 fpm.
HEPA filters fan-powered terminal modules
Air Filtration
61
Importance of Air change rates per hour (ACH).
Impact of ACH on fan sizing (construction cost)
and energy use.
Table 9: conflicting sets of recommendations.
ACH for some existing facilities: see Figure 11.
Air Change per Hour
62
Air Change per Hour
Many of the
recommended ACH are
based on relatively low-
efficiency filters that were
prevalent several years
ago.
Example ISO class 5:
from 250 to more than
700 air changes per hour
63
0
50
100
150
200
250
300
A B C D E F G H
Facilities
AirChangeperHour
Air Change per Hour
Fig. 11 Actual air change per hour for some existing
facilities of ISO Class 5 (see Rumsey2003)

17. 16
64
Air Change per Hour
65
Outline
Introduction
Standards & Classifications
Contamination
Testing
Types of Clean Areas
HVAC System Design
Air Flow Pattern
Air Filtration
Design Parameters
Air Distribution
T & RH Control
Pressurization Control
Validation Tests
HVAC System Cost
Other Design Consideration
Anterooms
66
Design parameters that are related to one another:
Room airflow velocity
The ceiling coverage
fraction
The number of air
changes per hour.
Relation between Air Flow Design
Parameter
67
Relation between Air Flow Design
Parameter

18. 17
68
Airflow velocity: 0.45 m/s or higher was used to assure
cleanliness level for ISO class 3, 4 or 5 in unidirectional
flow.
The air outlet velocity will be the same as the HEPA
filter face velocity
WLCuQ f3600=
Relation between Air Flow Design
Parameter
69
This gives a room airflow average velocity ur that is
expressed by the following equation
Relation between Air Flow Design
Parameter
CuWLQu fr == )3600/(
ACH :
HCuWLHQACH f
/3600)/( ==
70
Table 10 Calculated ACH, Q, and Ur for various ISO classes
ISO
Class
L W H Uf C Q Ur ACHC ACHR
m m m m/s m3/hr m/s
8 3 2 3 0.5 0.05 540 0.03 30 20-30
7 3 2 3 0.5 0.10 1080 0.05 60 45-60
7 3 2 3 0.5 0.20 2160 0.10 120 54-60
6 3 2 3 0.5 0.40 4320 0.20 240 120-150
6 3 2 3 0.5 0.50 5400 0.25 300 120-150
5 3 2 3 0.5 0.60 6480 0.30 360 400-480
5 3 2 3 0.5 0.80 8640 0.40 480 400-480
4 3 2 3 0.5 0.85 9180 0.43 510 540-600
4 3 2 3 0.5 0.90 9720 0.45 540 540-600
3 3 2 3 0.5 0.98 10584 0.49 588 540-600 71
Well Mixed Room Model
st
i
st
eC
s
k
etC −−
+−= )1()(
K
V
Q
V
Q
s f
o
f ++−= ηη )1(
G
V
Q
Ck o
of +−= )1( η
Modeling Prediction of Air Flow
Rate

19. 18
72
Clean Air Dilution Model:
Q
G
CC i +=
))(1()1( CC
Q
Q
CC of
o
fi −−+−= ηη
Modeling Prediction of Air Flow
Rate
73Fig 12 Well-mixed cleanroom model Schematic
Modeling Prediction of Air Flow
Rate
74
Modeling Prediction of Air Flow
Rate
Fig. 13 Model schematic of clean air dilution of cleanroom 75
Modeling Prediction of Air Flow
Rate
CFD Model

20. 19
76
Outline
Introduction
Standards & Classifications
Contamination
Testing
Types of Clean Areas
HVAC System Design
Air Flow Pattern
Air Filtration
Design Parameters
Air Distribution
T & RH Control
Pressurization Control
Validation Tests
HVAC System Cost
Other Design Consideration
Anterooms
77
HVAC Air Distribution System
Air Flow Rate
Requirements of airflow rate to a cleanroom:
1. Cooling/heating load
2. Moisture load
3. Contamination load
Cleanliness level is the controlling factor for low
clean class (i.e. cleaner rooms).
78
Alternative A: commonly used for ISO class 6 to 9.
Fig. 14 Alternative A: Supply air using AHU with HEPA air filter
Alternatives of Air Distribution
System
79
Alternative B:
Fig. 15 Alternative B: Supply air using AHU and air outlet HEPA filter
modules
Alternatives of Air Distribution
System

21. 20
80
Alternative C: appropriate for ISO class 9 to 6
Fig. 16 Alternative C: Supply air using primary AHU with cooling and /or
heating coil and Secondary AHU with HEPA air filter
Alternatives of Air Distribution
System
81
Alternative D: ISO clean class 5 or lower.
Alternatives of Air Distribution
System
Fig. 17 Alternative D: Supply air using AHU and Fan-powered HEPA filter
modules
82
Outline
Introduction
Standards & Classifications
Contamination
Testing
Types of Clean Areas
HVAC System Design
Air Flow Pattern
Air Filtration
Design Parameters
Air Distribution
T & RH Control
Pressurization Control
Validation Tests
HVAC System Cost
Other Design Consideration
Anterooms
83
Temperature and Relative
Humidity Control
Why to control T & RH
Controlling supply air temperature: Chilled water or
DX cooling coils
High limit of RH is usually the concern of RH control
in cleanrooms
Approaches to humidity control: air conditioning and
desiccants

22. 21
84
Outline
Introduction
Standards & Classifications
Contamination
Testing
Types of Clean Areas
HVAC System Design
Air Flow Pattern
Air Filtration
Design Parameters
Air Distribution
T & RH Control
Pressurization Control
Validation Tests
HVAC System Cost
Other Design Consideration
Anterooms
85
Cleanrooms: to avoid cross contamination with adjacent
spaces (when applied)
This can be achieved by keeping cleanroom:
at negative pressure, when the source of
contamination is inside the room, or
at positive pressure when the source of
contamination is outside
Pressurization Control
86
Pressurization Level:
Safety considerations: doors can be operated properly
and safely
Possibility for the pressurized space to implode,
blasting ceiling panels downward
To maintain accurate temperature and/or humidity
control it is desirable to minimize the quantity of air
being infiltrated to or ex-filtrated from the space.
Pressurization Control
87
Recommendation: 10 Pa between adjacent rooms of
different pressure levels
Methods to keep cleanrooms at a specified level of
pressurization.
Pressurization Control
Airflow supply and return/exhaust offset
Airflow tracking
Differential pressure control

23. 22
88
Airflow supply and return/exhaust
offset
Fig. 18 Pressurization using airflow supply and exhaust / return offset
89
Disadvantage: changing the pressurization level of
cleanroom by door opening/ closing.
Fig 19 Pressurization using airflow tracking
Airflow tracking
90
Using transfer grills
Airflow tracking
Fig 20 Controlling cleanroom pressure using adjustable gravity type
transfer grill (to be used only with airflow offset or airflow tracking
methods)
91
Differential pressure control
Fig 21 Pressurization using differential pressure control by
modulating either airflow supply or airflow return / exhaust

24. 23
92
Outline
Introduction
Standards & Classifications
Contamination
Testing
Types of Clean Areas
HVAC System Design
Air Flow Pattern
Air Filtration
Design Parameters
Air Distribution
T & RH Control
Pressurization Control
Validation Tests
HVAC System Cost
Other Design Consideration
Anterooms
93
HVAC Systems Validation Tests
Airflow velocity and uniformity
HEPA filter installation leak
Room airborne particle count t
Enclosure pressurization
Sound level measurements
Temperature and humidity uniformity
Recovery
Induction leak
Particle fallout count
94
Outline
Introduction
Standards & Classifications
Contamination
Testing
Types of Clean Areas
HVAC System Design
Air Flow Pattern
Air Filtration
Design Parameters
Air Distribution
T & RH Control
Pressurization Control
Validation Tests
HVAC System Cost
Other Design Consideration
Anterooms
95
Ready to use recipes for design:
Very common to avoid
potential design risks of
new approaches
Recipes usually lead to
higher construction cost
HVAC System Cost

25. 24
96
Major elements contributing to high design cost:
HVAC System Cost
Rate of Air Change per
Hour
Flow Pattern
Air Filtration Process
Sizing and
Specifications of Air
Handling Units
97
Table 10 Summary of Expected HVAC Construction Costs
Item ISO 3 ISO 5 ISO 7 ISO 8
Air change rate 0.19 Reference -0.072 -0.08
Airflow pattern 0.18 Reference -0.067 -0.073
Air filtration 0.10 Reference -0.028 -0.032
Air handling units 0.15 Reference -0.063 -0.07
Air pressure differential control 0.08 Reference -0.033 -0.041
Temperature control 0.15 Reference -0.026 -0.032
Humidity control 0.19 Reference -0.032 -0.034
Exhaust system 0.16 Reference -0.028 -0.031
Energy conservation 0.15 Reference -0.015 -0.017
Others 0.88 Reference -0.176 -0.2
TOTAL 2.23 Reference -0.54 -0.61
Construction cost
(Key Value Factor)
2.23 1 0.46 0.39
98
Relative Cost of HVAC System
0
0.5
1
1.5
2
2.5
ISO 3 ISO 5 ISO 7 ISO 8
ISO Class
RelativeCosttoISO5
Fig. 22 Relative HVAC cost of various ISO Classes to that of ISO 5
HVAC System Cost
99
Outline
Introduction
Standards & Classifications
Contamination
Testing
Types of Clean Areas
HVAC System Design
Air Flow Pattern
Air Filtration
Design Parameters
Air Distribution
T & RH Control
Pressurization Control
Validation Tests
HVAC System Cost
Other Design Consideration
Anterooms

26. 25
100
Select a sealed light fixture that prevents the
contamination of the cleanroom during
lighting, re-lamping and fixture
maintenance
Special design and shape of fixtures should
be used to avoid potential storage areas for
contaminants such as seams gaps between
parts.
Special types of light fixtures:
Additional Design Consideration
Lighting Cleanrooms
A light fixture that mounts on the
“T” grid
A flow through fixture that mounts
under the HEPA filter and allows
the clean air to pass through it.
101
Fig. 23 T drop light fixtures
Additional Design Consideration
Lighting Cleanrooms
102
Additional Design Consideration
Lighting Cleanrooms
Fig. 24 Flow-Thru light fixtures
103
Outline
Introduction
Standards & Classifications
Contamination
Testing
Types of Clean Areas
HVAC System Design
Air Flow Pattern
Air Filtration
Design Parameters
Air Distribution
T & RH Control
Pressurization Control
Validation Tests
HVAC System Cost
Other Design Consideration
Anterooms

27. 26
104
Anterooms
Location: adjacent to the
cleanroom
Function: to create an area in
close proximity to the
cleanroom where technicians
perform support tasks
Advantages: reduces the risk of
contamination in the cleanroom
Anteroom cleanroom rating:
usually Class 100,000,
depending on the risk level of
sterile products being prepared
in the critical
105