The N95 is the most popular series of particulate respirator masks that meet United States government standards. The face masks are tested to reduce exposure to airborne contaminates by NIOSH - the National Institiute for Occupational Safety and Health. NIOSH has nine total approval classes, N95, N99, N100, R95, R99, R100, P95, P99, P100 organized by oil compatibility and filter efficiency.
The letter signifies how the filter tests in environments exposed to oil aerosols:
N95, N99, & N100. These filters are not to be used with oil aerosols. These should be used in environments exposed to particulates which do not contain oil. In many cases, the n- respirators can be reused multiple times.
R95, R99, & R100. These filters are oil resistant. The r- respirators can be used in atmospheres containing particulates any solid or liquid hazard including oil-based hazards. These are one-time use n95 mask.
P95, P99, & P100. These filters are oil proof. These respirators can be used in any environment exposed to hazardous particulates. The p- respirators are subject to time of use limitations.
The filter efficiency number refers to the percentage of airborne particulates that were removed in testing: 95%, 99%, and 100%. If a mask is NIOSH approved then it will have a stamp of approval class printed on the respirator.
NIOSH approved masks also come in different sizes, and a well fitting mask is vitally important. When test-fitting an N95 mask or other particulate respirator mask, follow these easy steps:
1. Press the mask (respirator ) firmly against the face with the outside nosepiece on the bridge of your nose.
2. Stretch and position the top headband on the back of your head above your ears. Stretch the bottom headband over the head and position below your ears.
3. With both hands, mold the metal nosepiece to the shape of your nose.
4. To test fit, cup both hands over the respirator and exhale vigorously. If air flows around your nose, tighten the nosepiece: if air flows around the edges of the respirator, reposition the headbands to fit better and test again until there is no air leakage.
Before choosing the right mask, it is also suggested that you speak with experienced industrial safety personnel about an assessment of your particular environment.