NIOSH air filtration rating

NIOSH air filtration rating refers to the publications of National Institute for Occupational Safety and Health (NIOSH) of US government pertaining to respirators and masks worn to filter contaminated air, regardless of cause.

NIOSH RatingsEdit

The first part of the filter's classification uses the letters N, R, or P to indicate the filter's ability to function when exposed to petroleum.

  • "N" = not resistant to petroleum
  • "R" = somewhat resistant to petroleum
  • "P" = strongly resistant to petroleum

The second part lists the percentage of particles that the mask is certified to block (such as 95 or 97 percent).

The most common is N95,[1] which is recommended by the US Centers for Disease Control and Prevention (CDC) for most cases of air contamination. These filters are designed to seal tightly around mouth and nose and are made of material certified to block 95% of particles 0.3 μm or larger in diameter, roughly the size of a single virus[2] and include PM2.5.

They are however "...relatively difficult to breath through...",[2][3] and their full effectiveness also depends on a good fit - NIOSH recommends that each respirator wearer receive " initial fit test and annual fit tests thereafter".[4]

Contrast with plain surgical maskEdit

Plain surgical masks are standard for staff in hospital operating rooms, and often recommended to the public as part of avoiding seasonal flu.[4] They do not carry a NIOSH rating. They are designed to filter out relatively large particles, such as sputum droplets and hair - but the World Health Organization, Society for Healthcare Epidemiology of America, the Infectious Diseases Society of America, the Association for Professionals in Infection Control and Epidemiology, and the American College of Occupational and Environmental Medicine all recommend these except in cases of "high risk".[2]


  1. ^ "NIOSH-Approved Respirators". The National Personal Protective Technology Laboratory. Retrieved 1 October 2018.
  2. ^ a b c "Unmasking the Surgical Mask: Does It Really Work?". 5 October 2009. Retrieved 21 October 2015.
  3. ^ "CDC - NIOSH-Approved N95 Particulate Filtering Facepiece Respirators - 3M Suppliers List". 2018-06-28. Retrieved 2018-11-09.
  4. ^ a b Brosseau, Lisa. "N95 Respirators and Surgical Masks". NIOSH Science Blog. CDC. Retrieved 1 October 2018.