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9. Cleanroom Testing and Monitoring


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Title: 9. Cleanroom Testing and Monitoring

9. Cleanroom Testing and Monitoring
Purposes for initial test
  • Fulfill the design
  • working correctly and achieving the contamination
  • Bench-mark
  • establish the initial performance of the room to
    compare the results of routine check or
    contamination problem in the future.
  • Training the staff (most important)
  • initial testing is to familiarize and train the
  • Only opportunity to understand how their
    cleanroom works and learn the methods used to

initial test
  • Time
  • been built/ going to hand over/ reopen
  • Tested standards
  • ISO 14644-1.
  • Monitoring
  • to regularly check the room at the time
    intervals set by ISO 14644-2

Principles of Cleanroom Testing
  • Quantity
  • Turbulently dilute--air volume (supply and
  • Unidirectional remove air velocity
  • Direction (flow direction)
  • from clean area ? less-clean areas to minimise
    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.

Cleanroom Tests
  • 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
  • The air direction through doorways, hatches, etc.
    is from clean to less-clean.

  • 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.

  • Air movement control within the room
  • turbulently ventilated check that there are no
    areas within the room with insufficient air
  • 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
  • temperature
  • relative humidity
  • heating and cooling capabilities of the room
  • sound levels
  • lighting levels
  • vibration levels.

  • Guides provided by
  • the American Society Heating Refrigeration and
    Airconditioning Engineers (ASHRAE) in the USA,
  • the Chartered Institute of Building Services
    Engineers (CIBSE) in the UK.

Testing in Relation to Room Type and Occupation
  • 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---these occupancy states are
    discussed more fully in Section 3.4 of this book.

Re-testing to Demonstrate Compliance
  • The cleanroom checked intervals, these intervals
    being more frequent in higher specified rooms
    ISO 14644-2

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.
  • where appropriate, microbiological counts.

10. Measurement of Air Quantities and Pressure
  • 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

Air Quantities
  • Instruments
  • Hoods air supply volumes
  • Anemometers air velocities
  • Turbulently ventilated rooms
  • measured within the air conditioning ducts?
    Pitot-static tube

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 away from the filter of about 30cm
    (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
Thermal Anemometers
  • Principle Air passing through the head of the
    instrument? cooling effect ? the air velocity
    Fig.10.3 a bead thermistor (????????)
  • Low velocities can be measured with this type of

Differential Pressure Tests
  • The units
  • Pascals, inch water gauge are used (12Pa 0.05
    inch water gauge).
  • Pressure difference 10 or 15 Pa between clean
  • 15 Pa is commonly used between a cleanroom and an
    unclassified room,
  • 10 Pa between two cleanrooms.

  • Large openings
  • problems can occur when trying to achieve a
    pressure difference between areas connected by
    large openings, such as a supply tunnel. To
    achieve the suggested pressure drop
  • Very large air quantities through the tunnel
  • To accept a lower pressure difference

Apparatus for measuring pressure differences
  • Manometer
  • range of pressure difference of 0-60 Pa (0-0.25
    inch water)
  • inclined manometer magnehelic gauge electronic

Inclined manometer
  • works by pressure pushing a liquid up an inclined
  • small pressure changes in the inclined tube up to
    a pressure of about 60 Pa.
  • After that pressure, the tube moves round to the
    vertical measuring pressure differences can be in
    the 100 to 500 Pa range.

Methods of checking pressure differences
  • pressure differences between areas
  • adjusting the pressure differences
  • extract be reduced to increase the pressure, and
    increased to decrease it.
  • If manometers are not permanently installed, a
    tube from a pressure gauge is passed under the
    door, or through an open by-pass grille or damper
    into the adjacent area.
  • In some ventilation systems, the pressures within
    rooms are measured with respect to one reference
    point. When this type of system is being checked,
    the pressure difference across a doorway can be
    calculated by subtracting the two readings of the
    adjoining spaces.

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11. Air Movement Control Between and Within
  • 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

Contamination can be pushed into the cleanroom at
  • ceiling-to-wall interface
  • filter and lighting housings-to-ceiling
  • ceiling-to-column interface
  • the cladding of the ceiling support pillars
  • Service plenums and the entry of services into
    the cleanroom electrical sockets and switches,
    and other types of services providers.
    Particularly difficult to foresee and control in
    a negatively pressurized containment room.

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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.

Containment leak testing
  • Timing
  • handing it over to the user
  • major reconstruction work has been carried out
  • ISO 14644-2 lists the containment leak test as
    an optional test and suggest a re-testing
    interval of two years

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
  • 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 visualization
  • Objective sufficient clean air gets to the
    critical areas? qualitative methods
  • Visualization
  • Streamers
  • smoke or particle streams
  • Streamers (threads or tapes)
  • high surface-area-to-weight ratio, ex. recording
  • A horizontal flow 0.5 m/s (100 ft/min)? streamer
    45 to the horizontal
  • about 1m/s (200 ft/min)? almost horizontal.

smoke or particle streams
  • oil smoke ? contamination
  • Water vapour from solid C02 (dry ice) or by
    nebulizing water

putter and smoke tube'
  • Titanium tetrachloride (TiCl4)?produces acid ?
    corrodes some surfaces ?harmful to sensitive
    machinery or harm the operator's lungs.

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.

Air Movement in unidirectional flow
  • air moves in lines
  • Visualisation techniques smoke stream
  • Still picture

Air velocity and Direction measurement
  • A permanent record velocity and direction

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Recovery Test Method
  • A quantitative approach
  • A burst of test particles ?introduced into the
    area to be tested? mixed with their
    surroundings?the airborne particle count should
    be measured,
  • A useful endpoint is one-hundredth of the
    original concentration, and the time taken to
    reach there can be used as an index of efficiency.

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Ch. 12 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)
Gasket and casing leaks from filter inserted up
from cleanroom
Gasket leaks from filters inserted down from
Figure 12.4 Filter-housing gel seal method
Artificial Smoke and Particle Test
  • Cold-generated oils
  • Di-octyl phthalate (DOP)????????
  • oily liquid, potentially toxic effects, no longer
  • Di-octylsebacate (DOS)??????
  • ??
  • poly alpha olefin (PAO)????
  • ??

Cold-generated oil Test
Air oil particle
Laskin nozzle
air (high pressure)
0.5 mm
Air pump
Hot generated smokes
inert gas CO2
Evaporation chamber
oil smoke
0.3 mm
Hot oil smoke generator
Semiconductor manufacturing
  • 'outgassing'
  • chemical products harmful to filter
  • ??Polystyrene Latex Spheres (PLSs)
  • ???????(0.1 1mm)

Apparatus for Measuring Smoke Penetration
  • Photometer???
  • 28 1/min (1 ft3/min) of airborne particles
  • particles refract the light
  • electrical signal
  • concentration between 0.0001 µg/1 and 100 µg/1.

  • 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
  • Scan speed not more than 5cm/s
  • leaks media, filter case, its housing
  • 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

Ch. 13 Airborne Particle Counts
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 mass of particles

principle of Particle Counter
Particle Counter
Airborne particle counter flow rate 28 1/min
(1 ft3/min) of air size range regular 0.3 µm or
0.5 µm high-sensitivity 0.1 µm but with a
smaller air volume.
Check p-counter.pdf Opc-8240.pdf
Continuous Monitoring Apparatus for Airborne
  • sequential
  • simultaneous

Sequential monitoring system
Simultaneous monitoring system
best but most expensive
Particle Counting in Different Occupancy States
  • Occupancy state as built, at rest, operational.
  • cleanroom contractor 'as built'
  • rule of thumb as built room will be about one
    class of cleanliness cleaner than when

Measurement of Particle Concentrations (ISO
  • Principles The number of sampling locations must
    reflect the size of the room and its cleanliness.
  • The methods (a) number of sampling locations and
    (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

Airborne sampling volume
  • 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)

  • One or more samples at each location
  • The volume sampled at each location at least two
  • 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.

  • 4m x 5m size. ISO Class 3 in the 'as built'
    condition at a particle size of gt 0.1 µm.
  • Number of locations
  • A 4m x 5m. ? N v4x5 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.
  • ?Minimum volume 20/1000 x 1000 20 litres

  • particle counter flow rate of 28.3 liter/min,
  • i.e. 20liter, time 42 s
  • ISO 14644-1 requires a minimum sample time of 1
  • ? 1 minute

  • first part of the ISO requirement is therefore
  • As less than nine samples were taken? 95 UCL
    does not exceeded the class limit. ???

Calculation of 95UCL
  • the 'means of averages' M
  • M (580612706530553)/5 596
  • Standard deviation (s.d).
  • Standard deviation s.d.69
  • 95?UCL MUCL factor x (s.d/vn)
  • As number of locations is 5, the t-factor is 2.1.
  • ? 95? UCL for particles gt 0.1 µm 596 2.1 x
    69/v5 661lt1000

  • The cleanroom is therefore within the required
    class limit.
  • The way to avoid any 95 UCL problems is to
    always test more than nine points in the room

Ch.14 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 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

Inertial impaction samplers
  • Flow rate 30 to 180 litres/min (1 ft3/min to 6
    ft3/min) of air
  • Air ?Inertial impactors ? slit or hole ?
    accelerate (2030m/s)

Centrifugal air samplers
  • Air? rotating vane? centrifugal force ? agar

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  • The impaction surface is in the form of a plastic
    strip with rectangular recesses into which agar
    is dispensed

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

Membrane holder with filter
Microbial Deposition onto Surfaces
  • Indirect measurement?volumetric sampling
  • direct method? settle plate sampling

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
    (diameter90mm) containing agar medium ? opened
    and exposed ? time (45 hours) ?particles to
    deposit Petri dishes

Calculation of the likely airborne contamination
Microbial Surface Sampling
  • contact sampling
  • swabbing

Contact surface sampling
  • surface (flat)? RODAC (Replicate Organisms
    Detection and Counting) dishes Fig 14.5 are
    used?The agar is rolled over the cleanroom
    surface ?Micro-organisms stick to the agar
    ?incubated time and temperature? micro-organisms
    grow counted.

Contact Slides
  • uneven surfaces bud swab rubbed surface and then
    rubbed over an agar plate.

Copan Swab Rinse Kits
Personnel sampling
  • Personnel are the primary source of
    micro-organisms in a cleanroom.
  • The methods commonly used are
  • Finger dabs.
  • The person's fingers tips, or their gloved hand,
    is pressed or wiped on an agar plate and the
    number of micro-organisms ascertained.
  • Contact plates or strips.
  • The person's garments are sampled by pressing the
    plate or strip onto their clothing. This is best
    done as they come out of the cleanroom.
  • Body box.
  • If a person wearing normal indoor clothing
    exercises within a body box their dispersion rate
    of airborne micro-organisms can be ascertained.

  • Dip Slide

15. Operating a Cleanroom Contamination Control
  • considering the sources and routes of
    contamination within a cleanroom and how to
    control these.

Control contamination
  • assessing risk during manufacturing such as
    Fault Tree Analysis (FTA) and Failure Mode and
    Effect Analysis (FMEA). (Electrical and
    mechanical systems)

Hazard Analysis and Critical Control Point
(HACCP) system.
  • HACCP has a seven-step approach
  • Identify the sources of contamination in the
  • 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

  • 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.
  • Train the staff.

Identification of Sources and Routes of
  • Sources of contamination
  • dirty areas adjacent to the cleanroom
  • unfiltered air supply
  • room air
  • surfaces
  • people
  • machines, as they work
  • raw materials
  • containers
  • packaging.

Airborne and contact routes of transfer
  • The two main routes of transfer are airborne and
  • Airbone particles are small fibres, chips or
    cuttings fall directly on to the product.
  • Contact machines, containers, packaging, raw
    materials, gloves, clothes, etc.

Construction of a risk diagram
  • Risk diagram possible sources of contamination
    their main routes of transfer methods of
    controlling this transfer.
  • Figure 15.1 is an example of a risk diagram the
    manufacturing process has been shown

Sources and routes of particle and microbial
contamination in a cleanroom along with
preventative measures
Sources and routes of control associated with
process machinery.
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 higher than 12

Identification of Methods to Control Hazards
  • Identify the contamination hazards ?their degree
    of risk assessed? methods available to control

  • Figures 15.1 and 15.2 show methods that can be
    used to control the routes of spread of
    contamination. These are
  • HEPA or ULPA air filters ? supply air
  • Airborne contamination from areas outside the
    cleanroom? air moves from the cleanroom outward
  • The contamination from the floors, walls and
    ceiling ? cleaning
  • Peoples mouth, hair, clothing and skin?
    Cleanroom garments and gloves
  • Contamination from machines ? design of the
    machine, the use of exhaust air systems to draw
    the contamination away. Cleaning ? dirt on the
  • Raw materials, containers and packaging ? made
    from materials that do not generate
    contamination manufactured in an environment
    have minimal concentrations of contamination
    correctly wrapped to ensure that they are not
    contaminated during delivery

Sampling Methods to Monitor Hazards and Control
  • Monitoring
  • collection efficiency of sampling instruments
  • calibration of the instruments
  • determination that the hazard is of sufficient
    importance to need to be monitored
  • determination that the sampling method used is
    the best available for directly measuring the
    hazard, or its control method.

Establishing a Monitoring Schedule with Alert and
Action Levels
  • 'alert' and 'action' conditions 'warning' and
    'alarm' levels.
  • The 'alert' level should be set to indicate that
    the contamination concentrations are higher than
    might be expected, but are still under control.
  • The 'action' level should be set such that when
    it is exceeded there should be an investigation.
  • Analysing the monitoring results and setting
    'alert' and 'action' levels is quite a
    complicated subject if a statistical approach is
    used. Knowledge of statistical techniques,
    especially the use of trend analysis.

Verification and Reappraisal of the System
  • The method is correctly implemented ? rejection
    rate of the product measurement of the particle,
    or microbial, levels in samples of the final
    product. We can now reassess the following
  • the relative importance of the hazards
  • the necessity and the methods for controlling the
  • the effectiveness of the control methods
  • the correctness of the monitoring schedule
  • whether the 'action' and 'alert' levels should be
    lowered or raised.

  • An effective contamination control system will
  • (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.

Staff Training
  • They first arrive at the cleanroom
  • Train at regular intervals throughout their

16. Cleanroom Disciplines
  • source of contamination
  • micro-organisms
  • particles and fibres

People Allowed into Cleanrooms
  • Walking
  • produce 1,000,000 particles gt 0.5 mm
  • several thousand microbe-carrying particles per

  • Suggestions contain criteria that can
    discriminate against some personnel
  • Skin conditions skin cells, dermatitis, sunburn
    or bad dandruff.
  • Respiratory conditions coughing, sneezing
  • Biocleanroom
  • allergic conditions, which cause sneezing,
    itching, scratching, or a running nose
  • allergic to materials used in the cleanroom, (a)
    garments (polyester) (b) plastic or latex gloves,
    (c) chemicals acids, solvents, cleaning agents
    and disinfectants, and (d) products manufactured
    in the room, e.g. antibiotics and hormones.

Personal Items Not Allowed into the Cleanroom
  • General rule nothing should be allowed into the
    cleanroom that is not required for production
    within the room.

Prohibited items
  • food, drink, sweets and chewing gum
  • cans or bottles, smoking materials
  • radios, CD players, Walkmans, cell phones,
    pagers, etc.
  • newspapers, magazines, books and paper
  • pencils and erasers
  • wallets, purses and other similar items.

Disciplines within the Cleanroom
  • Within a cleanroom rules-of-conduct written
    procedures 'does and don'ts' posted in the
    change or production area
  • Air transfer
  • come in and out through change areas buffer
    zone not use emergency exit
  • Doors not be left open not be opened or closed
    quickly open inwards into the production room

Personnel behaviour
  • No Silly behaviour The generation of
    contamination is proportional to activity.
  • motionless 100,000 particles gt0.5 µm/min
  • head, arms and body moving 1,000,000 particles
    gt 0.5 mm/min
  • walking 5,000,000 particles gt 0.5 µm/min

Personnel?? product
  • position themselves correctly
  • not lean over the product
  • working in unidirectional air not between the
    product and the source of the clean air, i.e. the
    air filter.
  • 'No-touch' techniques should be devised from
    gloved hand onto the product.

  • Oil and skin particles would contaminate the
    wafer with catastrophic results.
  • not support material against their body
  • No personal handkerchiefs
  • Washing, or disinfection when required, of gloves
    during use should be considered.

Handling materials
  • The movement of materials between the inside and
    outside of a cleanroom should be minimized.
  • Waste material collected frequently into easily
    identified containers and removed frequently from
    the cleanroom.

Maintenance and Service Personnel
  • Enter a cleanroom with permission.
  • Maintenance be trained ? cleanroom techniques, or
    closely supervised when they are within the
  • Wear the same cleanroom clothing as cleanroom
  • Technicians should ensure they remove dirty
    boiler suits, etc. and wash their hands before
    changing into cleanroom clothing.

  • Tools ? cleaned and sterilized stored for sole
    used within the cleanroom Tools materials ? not
    corrode. ?Only the tools or instruments needed
    within the room should be selected,
    decontaminated, and put into a cleanroom
    compatible bag or container.
  • instructions or drawings can be photocopied onto
    cleanroom paper, or laminated within plastic
    sheets, or placed in sealed plastic bags.
  • Particle generating operations such as drilling
    holes, or repairing ceilings and floors should be
    isolated from the rest of the area. A localized
    extract or vacuum can also be used to remove any
    dust generated.

17. Entry and Exit of Personnel
  • 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.

  • The type of cleanroom clothing
  • contamination control is very important a
    coverall, hood, facemask, knee-length boots and
  • contamination is not as important less
    enveloping clothing such as a smock, cap and shoe

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
  • 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

Changing into Cleanroom Garments
  • The best method of changing into cleanroom
    garments is one that minimises contamination
    getting onto the outside of the garments.
  • The design of clothing change areas is divided
    into zones
  • Pre-change zone
  • Changing zone
  • Cleanroom entrance zone.

Approaching the pre-change zone
  • blow nose, go to the toilet
  • shoe cleaner
  • Sticky cleanroom mats or flooring two general

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Pre-change zone
  • street or factory clothes? removed
  • Watches and rings ?removed. Items such as
    cigarettes and lighters, wallets and other
    valuables should be securely stored.
  • Remove cosmetics and apply a suitable skin
    moisturizer (no chemicals used in the formulation
    cause contamination problems in the product being
  • Put on a pair of disposable footwear coverings,
    or change into dedicated cleanroom shoes.
  • wash the hands, dry them and apply a suitable
    hand lotion.
  • Cross over from the pre-entry area into the
    change zone.

Changing zone
  • The garments to be worn are selected.
  • A facemask and hood (or cap) is put on
  • Temporary gloves known as 'donning gloves' are
    sometimes used
  • The coverall (or gown) should be removed from its
    packaging and unfolded without touching the

Cleanroom entrance zone
  • rossover bench allows cleanroom footwear
    (overshoes or overboots) to be correctly put on.
  • Protective goggle can be put on. These are used
    not only for safety reasons but to prevent
    eyelashes and eyebrow hair falling onto the

  • The garments should be checked in a full-length
    mirror to see that they are worn correctly.
  • If donning gloves have been used they can be
    dispensed with now. They can, however, be kept on
    and a pair of clean working gloves put on top.
    Two pairs of gloves can be used as a precaution
    against punctures, although sensitivity of touch
    is lost.

  • Low particle (and if required, sterile) working
    gloves should now be put on. In some cleanrooms
    this task is left until the personnel is within
    the production cleanroom.

Exit Changing Procedures
  • When leaving a cleanroom, personnel will either
  • discard all their garments and on reentry use a
    new set of garments (this is normally only
    employed in an aseptic pharmaceutical cleanroom)
  • discard their disposable items, such as masks and
    gloves, but reuse their coverall, smock, etc. on
  • clothing ? rolled up footwear ? pigeon holes
  • The hood (or cap) can be attached to the outside
    of the coverall (or gown) ? hung up, preferably
    in a cabinet.
  • Garment bags can be used.

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18. Materials?Equipment and Machinery
Materials used in a cleanroom
  • For manufacturing
  • Packaging for the product
  • Process machinery and equipment
  • Tools used for the maintenance, calibration or
    repair of equipment and machinery
  • Clothing for personnel, such as suits, gloves and

  • Materials for cleaning, such as wipers and mops
  • Disposable items such as writing materials,
    labels and swabs.

Materials used in a cleanroom for manufacturing
  • pharmaceutical manufacturing containers and
  • microelectronics industry silicon wafers and
    process chemicals

Contamination on materials can be
  • particles
  • micro-organisms
  • chemicals
  • electrostatic charge
  • molecular outgassing.

Prohibited material
  • abrasives or powders
  • aerosol-producing cans or bottles
  • items made from wood, rubber, paper, leather,
    wool, cotton and other naturally occurring
    materials that break up easily
  • items made from mild steel, or other materials
    that rust, corrode or oxidise

  • items that cause problems when machined or
    processed, e.g. they may smoke or break up
  • paper not manufactured for use in cleanrooms.
  • pencils and erasers
  • paper correcting fluid
  • personal items listed in Section 16.2 should not
    be brought in by cleanroom personnel
  • disposable items such as swabs, tapes and labels
    that are not cleanroom compatible.

Transfer of Items and Small Pieces of Equipment
through an Airlock
  • Transfer area with a bench
  • door (uncontrolled area) ?opened and the person
    enters? The package should be placed on the
    'wrapped receiving' or 'dirtier' part of the
    pass-over bench

  • The wrapping is then cleaned and removed

  • The outer packaging is now removed and deposited
    into a suitable container. The item is then be
    placed on the 'wrapping removed' or 'clean' part
    of the bench

  • The person ?leave. The airlock may be left for a
    few minutes to allow the airborne contamination
    to come down to a concentration. Cleanroom
    personnel now enter the cleanroom and pick up
    items that have been left (Figure 18.6).

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Entry of Machinery
  • Machines, and other heavy and large bulky items
    of equipment, are occasionally taken in or out of
    a cleanroom.
  • The best solution to the movement of bulky items
    is to design the materials airlock to be large
    enough to allow the entry and exit of every piece
    of machine to be brought in or out of the room.

19. Cleanroom Clothing
  • Contamination source people ? clothing ? product
  • Cleanroom clothing originated from hospitals
  • Function reducing inert particles and
    microbe-carrying particles.

Sources and Routes of Inert Particle Dispersion
  • More activity ? more particles disperse
    Dispersion is dependent on the clothing worn, but
    can be in the range of 106 to 107 per minute for
    particles gt 0.5 µm, i.e. up to 1010 per day.
  • People may disperse particles from
  • Skin clothing they wear under cleanroom
    garments cleanroom clothing
  • mouth and nose.

Sources of particles and mechanisms of release
  • Skin People shed approximately 109 skin cells
    per day. Skin cells are approximately 33µm x 44
  • Skin cells
  • released onto clothing and laundered away
  • others are washed away in the bathtub or shower.
  • a large number are dispersed into the air.

Sources and routes of particles and microbe
containing particles from people
Skin surface showing skin cells and beads of
Clothing under cleanroom clothing
  • natural fabrics such as a cotton shirt, cotton
    jeans and woollen jersey?large quantities of
    particles. natural materials have fibres that are
    both short and break up easily.
  • synthetic fabric the particle challenge can be
    reduced by 90 or more.

Cotton fabric photographed through a microscope.
Magnification about 100 times
Cleanroom clothing
  • synthetic plastic materials such as polyester or

Routes of transfer of particles
  • Pores between 80µm and 100µm? The particles
    generated from the skin and the inner clothing
    therefore pass through easily.
  • Personnel move particles be pumped out of
    closures at the neck, ankles, wrists and zips.
    ?Secure closures tight
  • tears or holes, particles can easily pass

Microcolony of bacteria on surface of skin
Routes of microbial dispersion
  • The routes of transfer ?the same as with inert
  • the pores in the fabric
  • poor closures at the neck, sleeves and ankles
  • damage to the fabric, i.e. tears and holes.
  • expelled from the mouth speaking, coughing and
  • When males wear ordinary indoor clothing, the
    average rate being closer to 200 per minute.
    Females will generally disperse less.

Types of Cleanroom Clothing
  • Clothing designs
  • The most effective type
  • completely envelopes a person
  • be made from a fabric that has effective
    filtration properties
  • have secure closures at the wrist, neck and
  • The choice of clothing will depend on what is
    being produced in the cleanroom. A poorer
    standard of cleanroom may use a cap, zip-up coat
    (smock) and shoe covers

  • In a higher standard of cleanroom a one-piece
    zip-up coverall, knee-high overboots and a hood
    that tucks under the neck of the garment will be

Cleanroom fabrics
  • The most popular type of clothing is made from
    woven synthetic fabrics.
  • Non-woven fabrics, such as Tyvek, are used as
    single, or limited reuse, garments. They are
    popular for visitors and are used by builders
    when constructing the room. They are also popular
    in pharmaceutical manufacturing facilities in the
    USA. Membrane barrier fabrics, such as GoreTex,
    which use a breathable membrane sandwiched onto,
    or between, synthetic woven fabrics, are very
    efficient they are expensive, and hence are used
    in the higher standard rooms.

Garment construction
  • To prevent the raw edges
  • To minimise shedding, the zippers, fasteners and
    shoe soles should not chip, break up or corrode.
  • Choice of garments
  • IEST Recommended Practice RP-CC-003.2.

R recommended NR not
recommended AS application specific (NR)
not recommended in nonunidirectional flow Table
19.2 Garment systems for aseptic cleanrooms (IEST
RP CC-003.2)
Processing of Cleanroom Garments and Change
  • Processing
  • to be reused? cleanroom laundry? antistatic
    treatment and disinfection or sterilisation
  • Frequency of change
  • semiconductor industry ( the highest
    specification), changed once or twice a week.
  • fresh garments are put on every time personnel
    move into an aseptic pharmaceutical production

Body box a, metronome b, bacterial and particle
Comparison of clothing made from different fabrics
  • Bacterial dispersion (counts/min) in relation to

Particle dispersion rate per minute in relation
to fabric
20. Cleanroom Masks and Gloves
Dispersion from the month
  • sneezing, coughing and talking these droplets
    contain salts and bacteria.
  • Saliva particles and droplets about 1 to
    2000µm 95 of them lie being between 2 and
    100µm, with an average size of about 50µm
    bacteria in saliva is normally over 107 bacteria
    per ml.
  • A 100µm particle will drop 1 metre in about 3
    seconds, but a 10µm particle takes about 5

  • Drying time Particles of water 1000µm in
    diameter will take about 3 minutes to evaporate,
    a 200µm particle will take 7 seconds, a 100µm
    particle about 1.6 seconds and a 50 µm particle
    about 0.4 seconds.

  • Efficiencies of over 95 for particles expelled
    from the mouth are usually obtained by most
    masks. A loss in efficiency is caused by
    particles passing round the side of the mask, and
    much of this is due to small particles (reported
    to be lt 3µm in the dry state).

Number of inert and microbe-carrying particles
emitted by a person
Particles emitted when pronouncing the letter f
Face masks
  • surgical-style with straps and loops disposable

  • Consideration pressure drop across the mask
    fabric masks ? high filtration efficiency
    against small particles? give a high-pressure
    drop across the mask that causes the generated
    particles to be forced round the outside of the
    mask. ? 'veil' or 'yashmak' type, one of these
    types being exposed to show its shape in Figure
    20.4. The normal way it is worn is shown in
    Figure 20.5.

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Powered exhaust headgear
  • These provide a barrier to contamination coming
    from the head, as well as the mouth. The exhaust
    from the helmet and face-shield is provided with
    a filtered exhaust system so that contamination
    does not escape into the cleanroom. An example is
    shown in Figure 20.6.

Cleanroom Gloves
  • Hand contamination and gloves
  • There are two types of gloves associated with
  • Knitted or woven gloves are used for lower
    classes, i.e. ISO Class 7 (Class 10,000) and
    poorer areas, as well as undergloves. The knit or
    weave should be tight and a number of loose
    threads minimised.
  • Barrier gloves, which have a continuous thin
    membrane covering the whole hand are used in the
    majority of cleanrooms.

  • Cleanroom gloves are not usually manufactured in
    a cleanroom they therefore require cleaning
    before being used.
  • Gloves may be required in some cleanrooms to
    prevent dangerous chemicals, usually acids or
    solvents, attacking the operator's hands.
  • Some operator's skin is allergic to the materials
    that gloves are made from.
  • Other glove properties chemical resistance and
    compatibility, electrostatic discharge
    properties, surface ion contribution when wet,
    contact transfer, barrier integrity, permeability
    to liquids, heat resistance and outgassing.

Glove manufacturing process
  • Gloves are generally manufactured by dipping a
    'former' (porcelain or stainless steel), shape of
    a hand,? molten or liquid glove material? removed
    from the molten or liquid material? a layer of
    material? stripped by release agent? Release
    agents are a problem in cleanrooms ? Release
    agents kept to a minimum.
  • When stripped from the formers, latex gloves are
    'sticky'. To correct this, latex gloves are
    washed in a chlorine bath. The free chlorine
    combines chemically with the latex chemical bonds
    and lead to a 'case-hardening' of the surface of
    the glove, which prevents them sticking to each
    other. This washing also helps to clean to the

Types of gloves
  • Polyvinyl chloride (PVC) gloves
  • Latex Gloves
  • Other Polymer Gloves

Polyvinyl chloride (PVC) gloves
  • These plastic gloves are also known as vinyl
    gloves and are popular in electronic cleanrooms
    can not sterilised, not used in bioclean rooms.
  • They are available in normal and long-sleeve
    length. Consideration should be made of the fact
    that plasticisers make up almost 50 of a vinyl
    glove. Plasdcisers come from the same group of
    chemicals used to test the integrity of air
    filters, i.e. phthalates, antistatic properties,

Latex Gloves
  • This is the type used by surgeons, and the
    'particle-free' type is now used in cleanrooms.
    Latex gloves can be produced 'powder-free', and
    those gloves that are washed further by use of
    filtered, deionised water are often used in ISO
    Class 4 (Class 10) or ISO Class 3 (Class 1)
  • They have good chemical resistance, giving
    protection against most weak acids and bases, and
    alcohols, as well as having a fairly good
    resistance against aldehydes and ketones.
  • They are slightly more expensive to buy than the
    PVC type, but cheaper than any other polymer.
    They can be sterilised. Because of their
    elasticity, the glove can securely incorporate
    the cuff of a garment under the sleeve.

Other Polymer Gloves
  • Polythene gloves
  • are used in cleanrooms and have the advantage of
    being free of oils and additives, as well as
    resistant to puncturing. They are not resistant
    to aliphatic solvents. The main drawback of this
    glove type is that they are constructed from
    float sheets and the seams are welded. Manual
    dexterity is reduced with these gloves.
  • Neoprene and nitrile gloves
  • are chemically similar to latex gloves, but have
    the advantage of having a better resistance to
    solvents than latex gloves. They are slightly
    more expensive than latex.
  • Polyurethane gloves
  • are strong, very thin, quite inflexible, and
    expensive. They may be manufactured with
    microporous material for better comfort, or with
    carbon in the formulation which makes them
  • PVA gloves
  • are resistant to strong acids and solvents, but
    not water in which they are soluble. They are
  • Gore-Tex gloves
  • have welded seams and are hypoallergenic. They
    are breathable because of their porous membrane.
    They are expensive.

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21. Cleaning a Cleanroom
Why a Cleanroom Must be Cleaned?
  • Particles
  • cleanroom clothing, over 100,000 particles gt 0.5
    µm and over 10,000 particles gt 5.0µm.
  • Machines also disperse millions of particles.
  • Microbe-carrying particles People can also
    disperse hundreds, or thousands, of
    microbe-carrying particles per minute. Because
    these micro-organisms are carried on skin cells,
    or fragments of skin cells, their average
    equivalent diameter is between 10 µm and 20 µm.
  • Transfer Cleanrooms surfaces get dirty be
    transferred by personnel touching a cleanroom
    surface and then the product.

Cleaning Methods and the Physics of Cleaning
  • Forces hold particles to cleanroom surfaces
  • The main force the London-van der WaaPs force,
    this being an inter-molecular force.
  • Electrostatic forces can also attract particles
    to a surface.
  • A third force can arise after wet cleaning.
    Particles that are left behind will dry on the
    surface, and may adhere to it

  • The methods that are generally used for cleaning
    a cleanroom, are
  • Vacuuming (wet or dry) immersing the particle in
    a liquid, as occurs in wet pick-up vacuuming
  • Wet wiping (mopping or damp wiping) an
    aqueous-based detergent is used then the
    London-van der WaaFs force and electrostatic
    forces can be reduced or eliminated. The particle
    can then be pushed or drawn off from a surface by
    wiping, mopping or vacuuming.
  • Picking-up with a tacky roller.

  • Dry vacuuming
  • depends on a jet of air moving towards the vacuum
    nozzle and overcoming the adhesion forces of
    particles to the surface
  • Figure 21.1 efficiency of dry vacuuming against
    different sizes of sand particles on a glass
  • Wet vacuum Water and solvents have much higher
    viscosity than air, so that the drag forces
    exerted by liquids on a surface particle are very
    much greater.

Efficiency of dry vacuuming
  • Wet -wiping
  • Wet wiping, with wipers or mops, can efficiently
    clean cleanroom surfaces. The liquid used allows
    some of the particle-to-surface bonds to be
    broken and particles to float off.
  • Tacky rollers
  • The particle removal efficiency of 'tacky'
    rollers is dependent on the strength of the
    adhesive force of the roller's surface.

  • dry brush should never be used to sweep a
    cleanroom. they can produce over 50 million
    particles gt 0.5 µm per minute.
  • String mops are not much better, as they can
    produce almost 20 million particles gt 0.5 µm per

  • Dry vacuuming popular method
  • relatively inexpensive
  • no cleaning liquids are needed
  • Note unfiltered exhaust-air must not pass into
    the cleanroom. This is achieved by using either
    an external central-vacuum source, or providing a
    portable vacuum's exhaust air with a HEPA or ULPA

  • Wet vacuum or 'pick-up' system is more efficient
    than dry vacuum
  • more efficient than a mopping method,
  • less liquid left to dry on the floor
  • floor will also dry quicker.
  • Wet pick-up systems are used on conventionally
    ventilated cleanroom floors, but may not be
    suitable for the pass-though type of floor used
    in the vertical unidirectional system.

  • Mopping systems
  • mops for cleanroom
  • materials that do not easily
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