What Is an N95 Mask?

N95 respirators represent a U.S. certification standard for respiratory protective equipment, established and certified by the National Institute for Occupational Safety and Health (NIOSH). Under standardized environmental conditions—including specific temperature and humidity levels—these respirators filter at least 95% of airborne, non-oil-based particles (e.g., aerosols), tested at a specified airflow rate of 85 liters per minute; hence the designation “N95.”

What is an N95 respirator?

An N95 respirator filters at least 95% of very fine, non-oil-based particles with a diameter of 0.3 micrometers (µm). Respirators capable of filtering ≥95% of aerosolized particles are relatively uncommon in everyday use; those achieving ≥99% filtration efficiency are designated N99 respirators and offer superior protection.

N95 respirators provide excellent protection, effectively blocking virtually all respiratory droplets, making them suitable for routine preventive use. There is generally no need to use respirators with protection levels exceeding N95. Surgical masks may also be used for protection; their filtration efficacy against droplets is comparable to that of N95 respirators. However, surgical masks should typically be discarded after approximately four hours of continuous use and offer limited protection against air pollution (e.g., smog). In contrast, N95 respirators may remain effective for one to two days under normal conditions—but if labeled as “medical-grade,” they are intended for single-use and must be discarded promptly after use.

N95 respirators are designed for occupational respiratory protection, including defense against microbial aerosols such as viruses, bacteria, fungi, Bacillus anthracis, and Mycobacterium tuberculosis. A key feature of N95 respirators is their ability to protect against infection via splashes of patient bodily fluids or blood. The U.S. Occupational Safety and Health Administration (OSHA) mandates that healthcare personnel exposed to tuberculosis-causing bacteria wear respirators meeting at least the N95 standard.