Masks and Respirators for Medical Applications

Aerosol is a fine suspension made of liquid or solid particles suspended in air with a size range usually below 100 µm.  Airborne particles with a size less than 7 μm are considered hazardous as they are insoluble in body fluids. They reach the respiratory organ, lungs. Larger particles are of less concern as they usually settle out in the upper respiratory tract, from where normal lung clearance mechanisms remove them. Personal protection equipment against aerosols, such as respirators and masks are aimed at arresting particles of size smaller than 7 μm. Pathogenic microbial agents are viruses, bacteria, protozoa and fungi. This chapter describes the mechanism of filtration by fibrous media, the material and construction of face masks and N95 respirators, and tests to be carried out for respirators.