An N95 mask or N95 respirator is a particulate-filtering facepiece respirator that meets the U.S. National Institute for Occupational Safety and Health (NIOSH) N95 classification of air filtration, meaning that it filters at least 95% of airborne particles.
N: This is a Respirator Rating Letter Class. It stands for “Non-Oil” meaning that if no oil-based particulates are present, then you can use the mask in the work environment. Other masks ratings are R (resistant to oil for 8 hours) and P (oil proof).
95: Masks ending in a 95, have a 95 percent efficiency. Masks ending in a 99 have a 99 percent efficiency. Masks ending in 100 are 99.97 percent efficient and that is the same as a HEPA quality filter.
.3 microns: The masks filter out contaminants like dusts, mists and fumes. The minimum size of .3 microns of particulates and large droplets won’t pass through the barrier, according to the Centers for Disease Control and Prevention (CDC.)
Material: The filtration material on the mask is an electrostatic non-woven polypropylene fiber.
Valve: Some disposable N95 masks come with an optional exhalation valve. “The presence of an exhalation valve reduces exhalation resistance, which makes it easier to breathe (exhale,)” according to the CDC.