N95 respirators are the most common tight-fitting respirator used in healthcare and industrial settings. "N" means not resistant to oil; "95" means filters 95% of test particles (0.3 microns). Key requirements: employees must be fit-tested annually per OSHA (29 CFR 1910.134), medical clearance must be obtained before fit testing, and employees must perform a seal check each time they don the respirator. In healthcare settings, N95s are essential for protection against airborne pathogens like tuberculosis and during aerosol-generating procedures.