Air Shower

Design & functionality of Air Showers

Air showers are generally constructed from cleanroom-compatible steel or plastic materials and feature electronically-powered blowers, filters and high-pressure jet nozzle the latter being incorporated into the walls and ceiling of the chamber. Air, at velocities of 3,000 to 7,000 feet-per-minute (FPM), continuously streams from the jet nozzles for 30–45 seconds, effectively removing loose particulate matter. Personnel inside the enclosure will lift their arms and turn their bodies for uniform exposure to the air streams, a procedure usually specified in protocol. Air currents from the jets create shearing and flapping  forces, which lift and remove contaminants from both flat surfaces and the creases of garments. HEPA filtraton within the air shower is capable of removing 99.97% of particles greater than 0.3umdiameter.

Air is channeled within the air shower using a closed-loop system, where it is continuously re-circulated. Air is forced through a motorized filter/blower module into a large plemum, then into the shower through jet nozzles. Particle-laden, contaminated air is routed out of the shower compartment through floor vents  and returned to the filtration unit. This process ensures that only decontaminated air is used to remove particulates from personnel and other equipment, such as supply carts.

Often, air showers are equipped with air ionizers to reduce static electricity  , as large volumes of high-velocity air create electric charges Since laboratory equipment, electronic measuring instruments and many hi-tech manufactured goods can often be damaged by electrostatic discharge , ionizers are essential in rendering material surfaces electrically neutral prior to entering the cleanroom.

Safety

 interlocking mechanisms are a common air shower feature to prevent both exits from being opened simultaneously, which would allow outside air to enter a tightly controlled environment. This requires occupants to stay inside until the decontamination cycle has completed. For this reason, safety features such as emergency storp  are required by most safety administrations. Alternatively, the air shower may consist of a long tunnel not equipped with doors; personnel slowly walk through to reach the controlled area. Air handling equipment creates an isolated atmosphere using pressure differentials  to create fluid boundaries between the inner and outer environments.