A filtering facepiece N95 respirator Half-face<unk> -purifying respirator with combination P100 particulate filter (magenta) and organic vapor (black) cartridge A firefighter wearing an N95 filtering facepiece respirator. Note that, in this picture, the respirator is being worn incorrectly because the top strap should be above the ears and behind the head. The<unk>  is the U.S. National Institute for Occupational Safety and Health<unk> 's classification of filtering respirators. The<unk> s describe the ability of the device to protect the wearer from solid and liquid particulates in the<unk> . The certification and approval process for respiratory protective devices is governed by Part 84 of Title 42 of the Code of Federal Regulations (42 CFR 84). Respiratory protective devices so classified include<unk> -purifying respirators (APR) such as filtering facepiece respirators and chemical protective cartridges that have incorporated particulate filter elements. The classifications only cover the<unk>  of particles or aerosols, not the<unk> -purifying respirator's ability to remove chemical gasses and vapors from<unk> , which is regulated under 42 CFR 84 Subpart L. For more information see Cartridge (respirator). The classifications assume that the respirator is properly fitted.
NIOSH air filtration rating
Lung allocation score
Seinsheimer classification
SOFA score
Surfactant–albumin ratio
ThroLy score
Oxygen enhancement ratio
Alveolar gas equation