An Air Shower is designed to supply Class 100 HEPA filtered air at high velocity to remove particulate matter from the person entering the cleanroom. You may have noticed this in non-Cleanrooms as well but their importance is much more in a cleanroom.
Air Shower is a self-contained air chamber installed at the entrance to cleanrooms in order to minimize the amount of particulate contaminants entering the cleanroom. Personnel move through the air shower while particulate contaminants are washed off with high velocity HEPA-filtered air jets. The significance of this is that the high air velocity, of about 6000 FPM, ensures efficient scrubbing necessary to remove the particulate matter.
Contaminated air is then taken in through the base unit, filtered, and re-circulated into the chamber.