Which respirator provides 99% filtration efficiency against airborne particles?

Correct answer: C. N99

• A. N100 filters 99.97% — the highest efficiency in the series, effectively equivalent to a HEPA filter.
• B. N95 filters 95% of airborne particles and is the standard respirator for aerosol-generating procedures and for tuberculosis precautions in healthcare.
• C. CORRECT. The number in a respirator designation IS the filtration efficiency percentage against 0.3 micron particles. N99 filters 99%. The letter describes oil resistance: N = NOT resistant to oil, R = somewhat Resistant to oil, P = oil Proof.
• D. R95 also filters 95%, but is somewhat resistant to oil-based aerosols. The efficiency is identical to N95; only the oil resistance differs.

Note: Do not confuse a respirator with a SURGICAL MASK. A surgical mask is a fluid barrier that protects the patient from the operator's droplets and does not seal to the face. A respirator is FIT-TESTED to form a seal and filters inhaled air, which is why only a respirator protects against true airborne pathogens such as M. tuberculosis and measles. Facial hair breaks the seal and invalidates the protection.