Behavior of particles drifting in the air in a clean room and its effects on contamination [biomedical application]

The behavior of particles drifting in a clean room was pursued by a particle counter (Rion, KC-01A) under the several designed conditions. Where, density of particles is the number of particles over 0.5 μm in cubic feet (ft³) of air. The usual density of particles in the clean room was around 500 under the air filter operation. Outside of the room, it was about 250,000 in the air. When a person walked around in the clean room, density of particles did not exceed 1,000. Density of particles in the room D increased naturally according to the time t after the stop of filtering of air, that is, D=1,091.t+275(R=0.97). The increased particles were trapped within 5 minutes by air filter operation. For example, D=29,000 exp(-1.11.t). The initial density D was set as 29,200. When a person entered the room, density of particles reached over 3,000 in case of stopping air shower and leaving the door open for 5 minutes. In this case, the disastrous contamination will likely occur