NIOSH

NIOSH Standards for Respiratory Protection

NIOSH (the National Institute for Occupational Safety and Health) is the federal agency responsible for testing and certifying respirators before they can be sold for occupational use in the U.S., under the framework laid out in 42 CFR Part 84. This is where the familiar N95, N99, N100, R95, and P100 ratings come from: the letter (N, R, or P) indicates how the filter holds up against oil-based particles, and the number indicates the minimum percentage of airborne particles it filters out. A respirator that isn’t NIOSH-approved under 42 CFR 84 shouldn’t be relied on for occupational protection, no matter what it’s marketed as.