The National Institute for Occupational Safety and Health (NIOSH) is responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is also directly responsible for several regulations.

NIOSH issues recommendations for respirator use. Industrial type approvals are in accordance to the NIOSH federal respiratory regulations 42 CFR Part 84: Approval of respiratory protective devices. Development of respirator standards are in concert with various partners from government and industry.

In the United States, the National Institute for Occupational Safety and Health defines the following categories of particulate filters:

Oil resistance

Rating

     Description

Not oil resistant

N95

     Filters at least 95% of airborne particles

N99

     Filters at least 99% of airborne particles

N100

     Filters at least 99.97% of airborne particles

Oil Resistant

R95

   Filters at least 95% of airborne particles

R99

   Filters at least 99% of airborne particles

R100

   Filters at least 99.97% of airborne particles

Oil Proof

P95

   Filters at least 95% of airborne particles

P99

   Filters at least 99% of airborne particles

P100

   Filters at least 99.97% of airborne particles

NIOSH APPROVED: N95

95% efficient against particulate aerosols free of oil. This respirator helps protect against certain particulate contaminants but does not eliminate exposure to or the risk of contacting disease or infection. Misuse may result in sickness or death.