Disposable "Particulate" Respirators
Particulate respirators are also known as "air-purifying respirators" because they protect by filtering particles out of the air you breathe. Workers can wear any one of the particulate respirators for protection against diseases spread through the air - if they are NIOSH approved and if they have been properly fit tested and maintained.

Type     Description
N95     Filters at least 95% of airborne particles. Not resistant to oil.
N99     Filters at least 99% of airborne particles. Not resistant to oil.
N100     Filters at least 99.97% of airborne particles. Not resistant to oil.
R95     Filters at least 95% of airborne particles. Somewhat resistant to oil.
R99*     Filters at least 99% of airborne particles. Somewhat resistant to oil.
R100*     Filters at least 99.97% of airborne particles. Somewhat resistant to oil.
P95     Filters at least 95% of airborne particles. Strongly resistant to oil.
P99*     Filters at least 99% of airborne particles. Strongly resistant to oil.
P100     Filters at least 99.97% of airborne particles. Strongly resistant to oil.

* No NIOSH approvals are held by this type of disposable particulate respirator.