Principles of Cleanroom Testing and Monitoring
Cleanrooms:
Testing and Monitoring
Principles of Cleanroom Testing (pt. 1)
•
Quantity:
–
Turbulently: dilute--air volume (supply and extract)
–
Unidirectional: air velocity
•
Direction (flow direction):
–
from clean area
less-clean areas to minimize the
movement of contaminated air.
•
Quality:
–
the air will not add significantly to the contamination
within the room
•
Distribution inside cleanroom
–
the air movement has no areas with high concentrations
of contamination.
Principles of Cleanroom Testing (pt. 2)
•
Air supply and extract quantities
–
turbulently ventilated cleanrooms
the air supply
and extract volumes
–
unidirectional airflow
air velocity.
•
Air movement control between areas:
direction
–
The pressure differences between areas are correct.
–
The air direction through doorways, hatches, etc. is
from clean to less-clean.
Principles of Cleanroom Testing (pt. 3)
•
Filter installation leak test
–
a damaged filter
–
between the filter and its housing or
–
any other part of the filter installation.
•
Containment leak testing
–
Contamination is not entering the cleanroom
through its construction materials.
Principles of Cleanroom Testing (pt. 4)
•
Air movement control within the room
–
turbulently ventilated : check that there are no areas
within the room with insufficient air movement.
–
unidirectional airflow : check that the air velocity and
direction throughout the room is that specified in the
design.
•
Airborne particles and microbial concentrations
–
final measurements of the concentration of particles
and micro-organisms
Additional Tests
•
Additional tests include
–
temperature
–
relative humidity
–
heating and cooling capabilities of the room
–
sound levels
–
lighting levels
Testing in Relation to Room Type and
Occupation State
•
The type of tests to be carried out in a
cleanroom depends on whether the room is
unidirectional, turbulent or mixed airflow:
–
‘
as-built
---in the empty room,
–
‘
at rest
’
--- the room fitted with machinery
but no personnel present or
–
‘
fully operational
’
--- the occupancy state
Re-testing to Demonstrate Compliance
Monitoring of Cleanrooms
•
Use risk assessment to decide what monitoring tests
should be done and how often.
•
The variables that are most likely to be monitored
are:
–
air pressure difference
•
This might be necessary in high quality cleanrooms such as ISO
Class 4, and better.
–
airborne particle count
•
This might be necessary in high quality cleanrooms such as ISO
Class 4, and better.
–
microbiological counts, as appropriate
Measurement of Air
Quantities
and
Pressure Differences
Purpose
•
A cleanroom must have sufficient clean air supplied
to dilute and remove the airborne contamination
generated within the room.
•
Air Cleanliness:
–
Turbulently ventilated cleanroom
•
air supply; the more air supplied in a given time, the cleaner the
room.
–
unidirectional cleanroom
•
air supply velocity
•
Test:
–
Initial testing of the design
–
Regular intervals check
Measuring air quantities from within a
cleanroom
•
Air
air filter (no diffuser)
anemometer at the
filter face
average velocity
air volume
–
Difficulty: the non-uniformity of the air velocity
inaccurate measurement
•
Air
air diffusers
unevenness of air velocities
incorrect air volume
•
Hood: air supply volume
average velocity
measured at the exit of the hood
air volume
Anemometers
•
Anemometers: away from the filter of about
30 cm (12 inches)
•
Vane Anemometer
–
Principle: Air supply
turning a vane
frequency
velocity
–
Accuracy: velocity is less than about 0.2 m/s
(40 ft/min), the mechanical friction affects the
turning of the vane
Vane Anemometer
Also called windmill or a propeller anemometer.
Differential Pressure Tests (pt.1)
•
The units:
–
Pascals are used
–
12 Pa = 0.05 inch water gauge
•
Inch water column (inch WC)
is a unit for pressure.
•
It is used for measuring small pressure differences
across an orifice, or in a pipeline or shaft. Inches of
water can be converted to a pressure unit using the
formula for pressure head.
•
An
inch of water column
(iwc) is synonymous with an
inch of water gauge
(iwg).
•
It is defined as the pressure exerted by a column of
water of 1 inch in height at defined conditions.
•
1 iwg is approximately equal to 249 pascals at 0 °C
.
Differential Pressure Tests (pt. 2)
•
The units:
–
Pascals are used
–
12 Pa = 0.05 inch water gauge
•
Pressure difference: 10 or 15 Pa between
clean areas
–
15 Pa is commonly used between a cleanroom
and an unclassified room
–
10 Pa between two cleanrooms.
Apparatus for measuring pressure
differences
•
Manometer:
–
range of pressure
difference of 0-60 Pa (0-
0.25 inch water)
–
inclined manometer;
magnehelic gauge;
electronic manometer
Air Movement Control
Between and Within
Cleanrooms
Purposes
•
To show that a cleanroom is working correctly,
–
it is necessary to demonstrate that no
contamination infiltrates into the cleanroom from
dirtier adjacent areas.
•
Cleanroom Containment Leak Testing
–
Airborne contamination: doors and hatches, holes
and cracks in the walls, ceilings and other parts of
the cleanroom fabric
Methods of checking infiltration
•
Smoke test (dust test)
–
flow direction: open door, or through the cracks
around a closed door, cracks at the walls, ceiling,
floor and filter housings, service ducts or conduits.
•
Difficulty
–
where the containment originates from may be
unknown, and it is often difficult to find the places
to release test smoke.
Air Movement Control within a Cleanroom
•
sufficient air movement
–
dilute, or remove airborne contamination
prevent a build-up of
contamination
•
turbulently ventilated cleanroom:
–
good mixing, critical areas: where the product is exposed to the risk of
contamination
•
unidirectional flow cleanroom
–
critical areas should be supplied with air coming directly from the
high efficiency filters. However, problems may be encountered
because of:
•
heat rising from the machinery and disrupting the airflow
•
obstructions preventing the supply air getting to the critical area
•
obstructions, or the machinery shape, turning the unidirectional flow into
turbulent flow
•
contamination being entrained into the clean air.
Air Movement in turbulently ventilated
rooms
•
working well: quickly dispersed
•
not working well Areas
:
not disperse quickly
contamination build up
improved by
adjusting the air supply diffuser blades,
removing an obstruction, moving a machine.
Filter Installation Leak Testing
HEPA test
•
Manufacturer's factory and packed
OK
•
Unpacked and fitted into the filter housings
maybe damage
•
Leakage problems
–
casing
–
housing
•
Testing : artificial test aerosol
Leakage areas in a HEPA filter
A - filter paper-to-case cement area
C- gasket
D - frame joints.
B - filter paper (often at the paper fold)
Single Particle Counters
Sample a volume of air and this is collected in a set time
Methods of Testing Filters and Filter
Housings
•
Scanning methods
–
a probe with a photometer, or single particle
counter,
–
Scan speed : not more than 5 cm/s
–
The most common leaks:
•
around the periphery of the filter
•
the casing-to-housing seal,
•
the casing joints
Repair of leaks
•
Filter media leak
–
at the fold of the paper
–
repaired on site with
silicon
•
replaced
Cleanroom test
•
air supply volume,
•
pressure differences,
•
air movement within and between
cleanrooms,
•
filter integrity
•
airborne particle concentration
Particle counter
•
Particle counter :
–
Both
counts
and
sizes
•
Photometer :
–
Only
mass
of particles
flow rate: 28 1/min (1 ft
3
/min) of air
size range: regular 0.3 μm or 0.5 μm
high-sensitivity: 0.1 μm
Airborne particle counter:
Measurement of Particle Concentrations
(ISO 14644-1)
•
Principles: The number of sampling locations
must reflect the size of the room and its
cleanliness.
•
The methods:
–
(a) number of sampling locations
–
(b) the minimum air volume
Sample locations and number
(
ISO standard 14644-1
)
•
Minimum number of locations:
–
Where
N
L
rounded up to a whole
number
–
A
is the area of the cleanroom, or
clean air controlled space, in m
2
.
•
evenly
distributed and height
Airborne sampling volume (pt. 1)
•
Minimum volume at each location: the air
volume should be large enough to count
20
particles
of the largest particle size specified
•
V= 20/C x 1000
–
where V is the minimum single sample volume per
location, expressed in
litres
.
–
C is the class limit (number of particles/m3)
Airborne sampling volume (pt. 2)
•
One or more samples : at each location
•
The volume sampled at each location:
–
at least
two liters
•
The minimum sample time :
–
at least
one minute
Acceptance criteria ( ISO 14644-1)
•
the
average
particle concentration at each of the
particle measuring locations falls below the class
limit
•
when the total number of locations sampled is less
than
10
, the calculated
95% Upper Confidence
Limit (UCL)
of the particle concentrations is below
the class limit.
Example (pt. 1)
•
4m x 5m size. ISO Class 3 in the 'as built'
condition at a particle size of >= 0.1 μm.
•
Number of locations
–
A= 4m x 5m.
N = √4x5 = 4.47
5
–
The minimum number of locations is 5
•
Minimum air sampling volume
V= 20/C x 1000
C: ISO Class 3 room is 1000/m3.
Therefore:
Minimum volume = 20/1000 x 1000= 20 Litres
Example (pt. 2)
•
Particle counter flow rate of 28.3 liter/min,
i.e. 20 liter, time = 42 s
•
ISO 14644-1 requires a minimum sample time of
1 minute
•
1 minute
Example (pt. 3)
•
first part of the ISO requirement is therefore
satisfied(<1000).
OK
•
As less than nine samples were taken
95%
UCL does not exceeded the class limit.
???
Microbial Counts
•
People are normally the
only source
of micro-
organisms in a cleanroom
•
as built/ at rest
little value
•
Operational: micro-organisms are continually
dispersed from people in the room.
Microbial Sampling of the Air
•
Volumetric air sampler
•
Settle plate sampling
Volumetric air samplers
•
a given volume of air is sampled; also
known as 'active' sampling.
•
impact micro-organisms onto agar media;
•
remove micro-organisms by membrane
filtration.
Agar
•
Agar: jelly-type material with nutrients added
to support microbial growth.
•
Micro-organisms
landing
temperature,
time
colony (millimetres diameter)
Settle plate sampling
•
where micro-organisms are deposited, mainly
by gravity, onto an agar plate.
•
Impaction onto agar:
–
inertial impaction
–
centrifugal forces.
•
Time and Temperature to grow
•
Bacteria
:
48 hours at 30° C to 35° C;
•
Fungi
:
72 hours at 20° C to 25° C
Centrifugal air samplers
•
Air
rotating vane
centrifugal force
agar surface
Membrane filtration
•
A membrane filter is mounted in a holder
vacuum draw air
microbe-carrying will be
filtered out by membrane
The membrane
placed an agar plate
•
A membrane filter with a grid printed on the
surface will assist in counting the micro-
organisms.
Settle plate sampling
•
micro-organisms
skin particles
10 to
30μm
by gravity onto surfaces at an average
rate of about 1 cm/s
•
Settle plate sampling: Petri dishes
(diameter:90mm) containing agar medium
opened and exposed
time (4~5 hours)
particles to deposit Petri dishes
Microbial Surface Sampling
•
contact sampling
•
swabbing
Contact Surface sampling
•
Surface (flat)
•
RODAC (
Replicate
Organisms Detection and
Counting
) dishes are used
•
The agar is rolled over
the cleanroom surface
Micro-organisms stick to
the agar
•
incubated time and
temperature
•
micro-organisms grow
& counted.
Swabbing
•
uneven surfaces: bud
swab rubbed surface and
then rubbed over an agar
plate.
Purpose
•
Considering the sources and routes of
contamination within a cleanroom and how to
control these.
Operating a Cleanroom:
Contamination Control
Hazard Analysis and Critical Control Point
(HACCP)
System (pt. 1)
•
HACCP has a seven-step approach:
–
Identify the sources of contamination in the
cleanroom.
–
Assess the importance of these sources
–
Identify methods that can be used to control
these hazards.
–
Determine valid sampling methods to monitor
either the hazards, or their control methods, or
both.
Hazard Analysis and Critical Control
Point (HACCP)
System (pt. 2)
–
Establish a monitoring schedule with 'alert' and
'action' levels
•
Establish a monitoring schedule with 'alert' and 'action'
levels
–
Verify that the contamination control system is
working effectively by reviewing the product
rejection rate, sampling results and control
methods and, where appropriate, modifying them.
–
Establish and maintain appropriate
documentation.
Identification of Sources and Routes of
Contamination
•
Sources of contamination
–
dirty areas adjacent to the cleanroom;
–
unfiltered air supply;
–
room air;
–
surfaces;
–
people;
–
machines, as they work;
–
raw materials;
–
containers;
–
packaging.
Assessment of the Importance of Hazards
•
Possible sources of contamination
routes of
transmission
risk assessment
•
Risk factors:
–
risk factor A: the amount of contamination on, or in, the
source that is available for transfer
–
risk factor B: the ease by which the contamination is
dispersed or transferred
–
risk factor C: the proximity of the source to the critical
point where the product is exposed
–
risk factor D: how easily the contamination can pass
through the control method
Risk factors for assessing hazards
•
Risk rating = A x B x C x D
•
Low: A risk rating of
less
than 4
•
Medium:
between 4 and
12
•
High:
More than 12
Documentation
•
An effective contamination control system will
document
•
(1) the methods described in the preceding steps of
this chapter,
•
(2) the monitoring procedures, and
•
(3) results from the monitoring.
•
Regular reports should be issued of an analysis of the
monitoring results and any deviations from the
expected results.
•
•
Skin and clothing: millions of particles and
thousands of microbe-carrying particles
•
Features of cleanroom clothing:
–
not break up and lint: disperse the minimum of
fibres and particles
–
filter: against particles dispersed from the
person's skin and their clothing.
Entry and Exit of Personnel
Besides
Cleanroom Discipline
Prior to Arriving at the Cleanroom
•
Frequency of bathe or shower:
•
remove the natural skin oils;
•
dispersion of skin and skin bacteria;
•
dry skin may wish to use a skin lotion
•
What clothing is best worn below cleanroom garments?
•
Artificial fibres: polyester are better than those made from wool and
cotton
•
Close-woven fabrics: more effective in filtering and controlling the
particles and microbe-carrying particles
•
Cosmetics, hair spray, nail varnish
removed rings, watches
and valuables
removed and stored
Cleanrooms play a critical role in maintaining the quality of air and controlling contamination levels to ensure a sterile environment. The testing principles cover aspects such as air volume, velocity, direction, filter installation, air movement control, and additional tests like temperature and lighting levels. Understanding these principles is essential for ensuring effective cleanroom operation and compliance with quality standards.
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Presentation Transcript
Cleanrooms: Testing and Monitoring
Principles of Cleanroom Testing (pt. 1) Quantity: Turbulently: dilute--air volume (supply and extract) Unidirectional: air velocity Direction (flow direction): from clean area less-clean areas to minimize the movement of contaminated air. Quality: the air will not add significantly to the contamination within the room Distribution inside cleanroom the air movement has no areas with high concentrations of contamination.
Principles of Cleanroom Testing (pt. 2) Air supply and extract quantities turbulently ventilated cleanrooms the air supply and extract volumes unidirectional airflow air velocity. Air movement control between areas: direction The pressure differences between areas are correct. The air direction through doorways, hatches, etc. is from clean to less-clean.
Principles of Cleanroom Testing (pt. 3) Filter installation leak test a damaged filter between the filter and its housing or any other part of the filter installation. Containment leak testing Contamination is not entering the cleanroom through its construction materials.
Principles of Cleanroom Testing (pt. 4) Air movement control within the room turbulently ventilated : check that there are no areas within the room with insufficient air movement. unidirectional airflow : check that the air velocity and direction throughout the room is that specified in the design. Airborne particles and microbial concentrations final measurements of the concentration of particles and micro-organisms
Additional Tests Additional tests include temperature relative humidity heating and cooling capabilities of the room sound levels lighting levels
Testing in Relation to Room Type and Occupation State The type of tests to be carried out in a cleanroom depends on whether the room is unidirectional, turbulent or mixed airflow: as-built ---in the empty room, at rest --- the room fitted with machinery but no personnel present or fully operational --- the occupancy state
Re-testing to Demonstrate Compliance Test Parameter Class Max. Time Interval To demonstrate compliance by particle counting ISO 5 6 months >ISO 5 12 months Schedule of additional tests Airflow velocity of volume All classes 12 months Air pressure difference All classes 12 months Schedule of optional tests Installed filter leakage All classes 24 months Airflow visualization All classes 24 months Recovery All classes 24 months Containment leakage All classes 24 months Schedule of tests to demonstrate continuing compliance
Monitoring of Cleanrooms Use risk assessment to decide what monitoring tests should be done and how often. The variables that are most likely to be monitored are: air pressure difference This might be necessary in high quality cleanrooms such as ISO Class 4, and better. airborne particle count This might be necessary in high quality cleanrooms such as ISO Class 4, and better. microbiological counts, as appropriate
Measurement of Air Quantities and Pressure Differences
Purpose A cleanroom must have sufficient clean air supplied to dilute and remove the airborne contamination generated within the room. Air Cleanliness: Turbulently ventilated cleanroom air supply; the more air supplied in a given time, the cleaner the room. unidirectional cleanroom air supply velocity Test: Initial testing of the design Regular intervals check
Measuring air quantities from within a cleanroom Air air filter (no diffuser) anemometer at the filter face average velocity air volume Difficulty: the non-uniformity of the air velocity inaccurate measurement Air air diffusers unevenness of air velocities incorrect air volume Hood: air supply volume average velocity measured at the exit of the hood air volume
Anemometers Anemometers: away from the filter of about 30 cm (12 inches) Vane Anemometer Principle: Air supply turning a vane frequency velocity Accuracy: velocity is less than about 0.2 m/s (40 ft/min), the mechanical friction affects the turning of the vane
Vane Anemometer Also called windmill or a propeller anemometer.
Differential Pressure Tests (pt.1) The units: Pascals are used 12 Pa = 0.05 inch water gauge Inch water column (inch WC) is a unit for pressure. It is used for measuring small pressure differences across an orifice, or in a pipeline or shaft. Inches of water can be converted to a pressure unit using the formula for pressure head. An inch of water column (iwc) is synonymous with an inch of water gauge (iwg). It is defined as the pressure exerted by a column of water of 1 inch in height at defined conditions. 1 iwg is approximately equal to 249 pascals at 0 C.
Differential Pressure Tests (pt. 2) The units: Pascals are used 12 Pa = 0.05 inch water gauge Pressure difference: 10 or 15 Pa between clean areas 15 Pa is commonly used between a cleanroom and an unclassified room 10 Pa between two cleanrooms.
Apparatus for measuring pressure differences Manometer: range of pressure difference of 0-60 Pa (0- 0.25 inch water) inclined manometer; magnehelic gauge; electronic manometer
Air Movement Control Between and Within Cleanrooms
Purposes To show that a cleanroom is working correctly, it is necessary to demonstrate that no contamination infiltrates into the cleanroom from dirtier adjacent areas. Cleanroom Containment Leak Testing Airborne contamination: doors and hatches, holes and cracks in the walls, ceilings and other parts of the cleanroom fabric
Methods of checking infiltration Smoke test (dust test) flow direction: open door, or through the cracks around a closed door, cracks at the walls, ceiling, floor and filter housings, service ducts or conduits. Difficulty where the containment originates from may be unknown, and it is often difficult to find the places to release test smoke.
Air Movement Control within a Cleanroom sufficient air movement dilute, or remove airborne contamination prevent a build-up of contamination turbulently ventilated cleanroom: good mixing, critical areas: where the product is exposed to the risk of contamination unidirectional flow cleanroom critical areas should be supplied with air coming directly from the high efficiency filters. However, problems may be encountered because of: heat rising from the machinery and disrupting the airflow obstructions preventing the supply air getting to the critical area obstructions, or the machinery shape, turning the unidirectional flow into turbulent flow contamination being entrained into the clean air.
Air Movement in turbulently ventilated rooms working well: quickly dispersed not working well Areas: not disperse quickly contamination build up improved by adjusting the air supply diffuser blades, removing an obstruction, moving a machine.
HEPA test Manufacturer's factory and packed OK Unpacked and fitted into the filter housings maybe damage Leakage problems casing housing Testing : artificial test aerosol
Leakage areas in a HEPA filter A - filter paper-to-case cement area C- gasket D - frame joints. B - filter paper (often at the paper fold)
Single Particle Counters Sample a volume of air and this is collected in a set time
Methods of Testing Filters and Filter Housings Scanning methods a probe with a photometer, or single particle counter, Scan speed : not more than 5 cm/s The most common leaks: around the periphery of the filter the casing-to-housing seal, the casing joints
Repair of leaks Filter media leak at the fold of the paper repaired on site with silicon replaced
Cleanroom test air supply volume, pressure differences, air movement within and between cleanrooms, filter integrity airborne particle concentration
Particle counter Particle counter : Both counts and sizes Photometer : Only mass of particles
Airborne particle counter: flow rate: 28 1/min (1 ft3/min) of air size range: regular 0.3 m or 0.5 m high-sensitivity: 0.1 m
Measurement of Particle Concentrations (ISO 14644-1) Principles: The number of sampling locations must reflect the size of the room and its cleanliness. The methods: (a) number of sampling locations (b) the minimum air volume
Sample locations and number (ISO standard 14644-1) Minimum number of locations: Where NL rounded up to a whole number A is the area of the cleanroom, or clean air controlled space, in m2. evenly distributed and height NL= A
Airborne sampling volume (pt. 1) Minimum volume at each location: the air volume should be large enough to count 20 particles of the largest particle size specified V= 20/C x 1000 where V is the minimum single sample volume per location, expressed in litres. C is the class limit (number of particles/m3)
Airborne sampling volume (pt. 2) One or more samples : at each location The volume sampled at each location: at least two liters The minimum sample time : at least one minute
Acceptance criteria ( ISO 14644-1) the average particle concentration at each of the particle measuring locations falls below the class limit when the total number of locations sampled is less than 10, the calculated 95% Upper Confidence Limit (UCL) of the particle concentrations is below the class limit.
Example (pt. 1) 4m x 5m size. ISO Class 3 in the 'as built' condition at a particle size of >= 0.1 m. Number of locations A= 4m x 5m. N = 4x5 = 4.47 5 The minimum number of locations is 5 Minimum air sampling volume V= 20/C x 1000 C: ISO Class 3 room is 1000/m3. Therefore: Minimum volume = 20/1000 x 1000= 20 Litres
Example (pt. 2) Particle counter flow rate of 28.3 liter/min, i.e. 20 liter, time = 42 s ISO 14644-1 requires a minimum sample time of 1 minute 1 minute
Example (pt. 3) first part of the ISO requirement is therefore satisfied(<1000). OK As less than nine samples were taken 95% UCL does not exceeded the class limit. ???
Microbial Counts People are normally the only source of micro- organisms in a cleanroom as built/ at rest little value Operational: micro-organisms are continually dispersed from people in the room.
Microbial Sampling of the Air Volumetric air sampler Settle plate sampling
Volumetric air samplers a given volume of air is sampled; also known as 'active' sampling. impact micro-organisms onto agar media; remove micro-organisms by membrane filtration.
Agar Agar: jelly-type material with nutrients added to support microbial growth. Micro-organisms landing temperature, time colony (millimetres diameter)
Settle plate sampling where micro-organisms are deposited, mainly by gravity, onto an agar plate. Impaction onto agar: inertial impaction centrifugal forces. Time and Temperature to grow Bacteria : 48 hours at 30 C to 35 C; Fungi: 72 hours at 20 C to 25 C
Centrifugal air samplers Air rotating vane centrifugal force agar surface
Membrane filtration A membrane filter is mounted in a holder vacuum draw air microbe-carrying will be filtered out by membrane The membrane placed an agar plate A membrane filter with a grid printed on the surface will assist in counting the micro- organisms.
Settle plate sampling micro-organisms skin particles 10 to 30 m by gravity onto surfaces at an average rate of about 1 cm/s Settle plate sampling: Petri dishes (diameter:90mm) containing agar medium opened and exposed time (4~5 hours) particles to deposit Petri dishes
Microbial Surface Sampling contact sampling swabbing
Contact Surface sampling Surface (flat) RODAC (Replicate Organisms Detection and Counting) dishes are used The agar is rolled over the cleanroom surface Micro-organisms stick to the agar incubated time and temperature micro-organisms grow & counted.
Swabbing uneven surfaces: bud swab rubbed surface and then rubbed over an agar plate.
