1.2 Respirators
Respirators either filter the airborne particles and respiratory aerosol; or supply clean air to the respirator wearer; air-purifying, or atmosphere-supplying respirators. The most common respirators are filtering facepiece respirators and powered air-purifying respirators (PAPR).
The National Institute for Occupational Safety and Health (NIOSH) tests filters for the effects of loading (particle burden), temperature, and relative humidity and requires minimum filtration efficiency of 95%, 99%, or 99.97% using neutralized 0.075µm count median diameter solid aerosols at 85L/min.(68) NIOSH evaluates the fit performance of some respiratory protective devices using human panels with specified facial dimensions.