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Cleanroom Airlock and Shower Technology
TIME : 2010-01-08

Cleanroom Airlock and Shower Technology

Cleanrooms are highly controlled locations where scientists and manufacturers can conduct experiments and build products and machinery without the interference of particle dust. Cleanrooms are necessary due to the near-sterile environment needed for production of sensitive items, like aerospace equipment and semi-conductors, as well as for experiments and research conducted with very sensitive materials. Microscopic particles in the air are difficult to control, but cleanrooms employ several systems in order to lessen the air’s particle content, including rigorous cleaning routines, the use of sterile materials, air filtering units, air showers, and air locks.

Cleanroom Classifications

There are three basic codes of classification for cleanrooms, but as International Organization for Standardization (ISO) codes are the most commonly used, this article will rely on them. ISO classifies cleanrooms on a scale from 1 to 9, with 1 being the “cleanest” air. ISO classification 1 cleanrooms have a maximum of 10 particles smaller than 0.1 micrometers in a cubic meter of airspace. Class 9 is used to describe normal room air. Cleanrooms are kept free of air particles through a variety of methods, including interior HEPA air conditioning and the sealing off of the work space with air locks at entrances and exits.

Air Showers and Air LocksHEPA filter in use

As Victor Mora, supervisor of the Flight System Integration and Test Flight Systems Section of NASA says, “Humans are the dirtiest things that enter a cleanroom.” But because a research and operations staff is an obvious necessity, precaution should be taken to prevent the introduction of foreign particles into the sterile environment. In order to accomplish this difficult goal, each cleanroom has a wide array of protective garments, gloves, shoe coverings, masks and hoods for cleanroom workers to put on prior to entering a cleanroom. This clothing change is performed in a clean environment, where workers remove all accessory items and cover their clothes with impermeable suits. Often, the floors will be sticky to attract particles from shoe bottoms.

Once workers have donned cleanroom suits, they will pass through an air shower. An air shower often looks very similar to a standard water shower, but it blows pressurized air at high velocity (as high as 3000 fpm) instead of liquid. The cleanroom worker stands underneath the air shower and receives a blast of air, which clears off particles that might have been obtained while dressing or settled on clothing in the non-sterilized changing location. The floors in an air shower facility might be sticky as well to collect particles missed by the previous floor.

After the air shower, the worker will sometimes have to pass through an airlock, depending on the classification of the cleanroom. Higher numbers indicate a cleanroom that is not fully sterilized, so some amount of particles may pass through. However, if a cleanroom has a lower ISO classification, an airlock is necessary. Airlocks are used for cleanrooms as an additional line of defense against foreign particles. When one room is isolated from both the outside world and the cleanroom, it can be flushed with air to expel any lingering particles.

HEPA Filters

Most cleanrooms utilize high efficiency particulate air (HEPA) filters to clean the air both in the cleanroom itself as well as in air lock facilities. These are high-efficiency air filters that employ fibers to help catch particles in one of three ways. The first is by intercepting particles, using the fibers. The second method is impaction, in which particles follow airflow lead and crash into fibers. Finally, there is diffusion, in which airflow direction prevents very tiny particles are prevented from forward motion and are not stopped, but forced to remain in the filters airstream.

Cleanrooms are highly controlled locations where scientists and manufacturers can conduct experiments and build products and machinery without the interference of particle dust. Cleanrooms are necessary due to the near-sterile environment needed for production of sensitive items, like aerospace equipment and semi-conductors, as well as for experiments and research conducted with very sensitive materials. Microscopic particles in the air are difficult to control, but cleanrooms employ several systems in order to lessen the air’s particle content, including rigorous cleaning routines, the use of sterile materials, air filtering units, air showers, and air locks.

Cleanroom Classifications

There are three basic codes of classification for cleanrooms, but as International Organization for Standardization (ISO) codes are the most commonly used, this article will rely on them. ISO classifies cleanrooms on a scale from 1 to 9, with 1 being the “cleanest” air. ISO classification 1 cleanrooms have a maximum of 10 particles smaller than 0.1 micrometers in a cubic meter of airspace. Class 9 is used to describe normal room air. Cleanrooms are kept free of air particles through a variety of methods, including interior HEPA air conditioning and the sealing off of the work space with air locks at entrances and exits.

Air Showers and Air Locks

As Victor Mora, supervisor of the Flight System Integration and Test Flight Systems Section of NASA says, “Humans are the dirtiest things that enter a cleanroom.”  But because a research and operations staff is an obvious necessity, precaution should be taken to prevent the introduction of foreign particles into the sterile environment. In order to accomplish this difficult goal, each cleanroom has a wide array of protective garments, gloves, shoe coverings, masks and hoods for cleanroom workers to put on prior to entering a cleanroom. This clothing change is performed in a clean environment, where workers remove all accessory items and cover their clothes with impermeable suits. Often, the floors will be sticky to attract particles from shoe bottoms.

Once workers have donned cleanroom suits, they will pass through an air shower. An air shower often looks very similar to a standard water shower, but it blows pressurized air at high velocity (as high as 3000 fpm) instead of liquid. The cleanroom worker stands underneath the air shower and receives a blast of air, which clears off particles that might have been obtained while dressing or settled on clothing in the non-sterilized changing location. The floors in an air shower facility might be sticky as well to collect particles missed by the previous floor.

After the air shower, the worker will sometimes have to pass through an airlock, depending on the classification of the cleanroom. Higher numbers indicate a cleanroom that is not fully sterilized, so some amount of particles may pass through. However, if a cleanroom has a lower ISO classification, an airlock is necessary. Airlocks are used for cleanrooms as an additional line of defense against foreign particles. When one room is isolated from both the outside world and the cleanroom, it can be flushed with air to expel any lingering particles.

HEPA Filters

Most cleanrooms utilize high efficiency particulate air (HEPA) filters to clean the air both in the cleanroom itself as well as in air lock facilities. These are high-efficiency air filters that employ fibers to help catch particles in one of three ways. The first is by intercepting particles, using the fibers. The second method is impaction, in which particles follow airflow lead and crash into fibers. Finally, there is diffusion, in which airflow direction prevents very tiny particles are prevented from forward motion and are not stopped, but forced to remain in the filters airstream.

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