Cleanroom vocabulary can be confusing. We explain the meaning of 27 commonly used cleanroom terms such as PAL, MAL, air shower, bunny suite and magnehelic gauge.
Air changes per hour: ISO-14644-1 sets requirements for cleanroom classifications. In addition to particles/meter3 , there is a requirement for air charges per hour of HEPA Filtered Air. The more air changes per hour the cleanroom the room. ISO-8 requires 20 air changes per hour. ISO-7 requires 60 air changes per hour. ISO-6 requires 180 air changes per hour. ISO-5 requires 250 to 300 air changes per hour.
Air shower: A cleanroom air shower uses high velocity HEPA filtered air to blow dirt off personnel before they enter the cleanroom. The worker changes into his/her bunny suit then enters the air shower. The air shower typically blows them off for 30 seconds, after which they enter the cleanroom.
Figure 2. Cleanroom air shower
As-built cleanroom particle test is particle testing when cleanroom has just been completed. It typically does not have equipment or personnel in the room.
At-rest cleanroom particle test is testing when the cleanroom has been in use and has equipment but no personnel are present and no operations are on-going.
Booties: Cleanroom booties are fabric shoe covers that are worn in cleanrooms to prevent personnel from tracking dirt in cleanroom. They are made from non particulating fabric. Some booties only cover your shoe and others extend up to your knee. They can be disposable or washable.
Figure 3. Disposable cleanroom booty.
Bunny suit: cleanroom bunny suits are protective non particulating coveralls and hoods that are designed to encapsulate all operator dirt inside the suit so operators do not give off any particulate in the cleanroom.
Figure 4. Cleanroom bunny suit
Cleanroom ceiling tiles: These are ceiling tiles coated with vinyl so they are washable and don’t introduce particles into the cleanroom. They also can be manufactured from FRP, painted aluminum, and stainless steel.
Figure 5. Cleanroom ceiling with vinyl coated cleanroom ceiling tiles
Cleanroom classification: ISO-14644-1 cleanroom classification specifies particle counts by size for each cleanroom class (meters3). Fed Std 209E is an older standard (ft3). There is also EU GMP Annex.
ISO 14644-1 Cleanroom Standards | Cleanroom Classifications
De-ionizer: Many products manufactured in cleanrooms are vulnerable to Electro Static Discharge (ESD) damage. Cleanrooms can be high static environments due to ions caused friction from air passing through the HEPA filters. De-ionizers create opposite charged ions to neutralize the HEPA filter ions.
Figure 6. Cleanroom de-ionizer system
Fed209E: This a US cleanroom classification system that was created for the electronics industry. It measures particles per ft3.
Humidistat: Some cleanrooms require humidity control. A humidistat measures the relative humidity of air in cleanroom and typically controls the cleanroom humidifier and/or dehumidifier.
Interlocks: Door interlock systems are used to prevent both doors in airlocks from being opened at same time. This prevents dirt from entering a cleanroom from outside. Cleanroom interlock systems typically consist of door sensors, magnetic locks, and PLC controller.
ISO-14644-1: Document that defines cleanliness requirements for cleanroom classes based on quantity and size of particles in a cubic meter if space.
Laminar flow: The two extremes of air flow are turbulent which one can equate with white water racing through rapids and laminar flow which is like a smooth stream with a mirror surface. In turbulent flow the air is moving in all directions raising particles into the air while in laminar flow the air flows smoothly downward pushing particles to the floor.
Magnehelic gauge: These are differential pressure gauges that are used to measure the difference in air pressure between the cleanroom vs. exterior and between individual cleanrooms. They typically measure in inches of water.
Figure 7. Cleanroom magnehelic gauge
MAL: Stands for Material Air Lock. MAL is an ante room that is used to transfer material into and out of cleanrooms. It typically has HEPA filtration and door interlocks.
Non-viable particles: In cleanrooms operators measure density of both live particles (bacteria, virus, mold etc.) and dead particles (dust, powders, etc.) per cubic meter. Nonviable means dead particles which are measured using a laser particle counter.
One pass cleanroom: This type of cleanroom draws air from outside, cleans it via HEPA filters, passes it through the cleanroom and then exhausts it back outside of cleanroom.
Figure 8. One pass cleanroom simulation
Operational cleanroom particle test is testing when personnel are in the cleanroom working and operating equipment.
PAL: Stands for Personnel Air Lock. PAL is an ante room that is used by personnel to enter and exit the cleanroom. It typically has HEPA filtration and door interlocks.
Particle counter: Particle counters should be used to measure particle density in cleanrooms. They use a laser to measure quantity and size of particles in a cleanroom.
Figure 9. benchtop cleanroom particle counter
Pass thru: these are boxes that are used to pass material into and out of cleanroom. The doors are interlocked so only one door can be opened at a time to prevent particles from entering the cleanroom.
Figure 10. 2’x2’ wall mounted pass thru
Recirculating cleanroom: In this type of cleanroom the air passes through the cleanroom then back up thru low wall air returns the plenum where it is cooled and then pulled by HEPA fan filter units back into the cleanroom. The air continuously recirculates, getting cleaner and cleaner.
Figure 11. Recirculating cleanroom simulation
Softwall cleanroom: These cleanrooms use clear vinyl curtains as walls. They are one pass and cannot have air conditioning.
Figure 12. Softwall cleanroom
Tacky Mat: These are sticky mats placed at the entrance to the cleanroom or gown room to remove any dirt on bottom of shoes.
USP797/800: U.S. Pharmacopeia (USP) is non-profit organization that recommends standards for compounding pharmacies in United States. USP797 is for sterile and non-sterile compounding. USP800 is for hazardous compounding (for example chemotherapy drugs). USP 797 cleanrooms typically have ISO-7 cleanrooms, ISO-8 gown rooms, pass thru’s and ISO-5 glove boxes. USP 800 cleanrooms are similar but are negative pressure so any hazardous particulates are exhausted out of cleanroom.
Viable particles: These particles in a cleanroom are alive . Examples are bacteria, virus, mold etc. Settling plates are placed in cleanroom to collect these particles for a set amount of time. The plate is then sent to a laboratory to be incubated and the number of live particles to be counted.
Figure 13. Cleanroom settling plate
Summary: This cleanroom dictionary covers 27 key terms used in the cleanroom industry including “air changes per hour”, “booties”, “bunny suit”, “Cleanroom classification, “cleanroom ceiling tiles”, “de-ionizer”, “Fed209E”, humidistat, interlock, ISO 14644-1, Laminar flow, magnehelic gauge, MAL, non-viable particles, operational particle test, PAL, Particle counter , Pass thru, recirculating cleanroom, Softwall cleanroom Tacky mat, USP797, and Viable particles.
Author: The author Anthony Chien has worked at American Cleanroom Systems for past 12 years. He has more than 40 years of cleanroom experience. Anthony has a BS and MS in Electrical Engineering specializing in semiconductor manufacturing from the University of Illinois. American Cleanroom Systems is a design build modular cleanroom manufacturer based in Rancho Santa Margarita CA. It is expert in ISO-5 through ISO-8 (class 100 to class 100k) modular cleanrooms for pharmaceutical cleanrooms, medical device cleanrooms, and industrial cleanrooms.
American Cleanroom Systems® 2024 - Unauthorized use and/or duplication of this material without express and written permission from this website owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to American Cleanrooms with appropriate and specific direction to the original content.
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