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.
Contents
Plain surgical mask
Plain surgical masks do not carry a NIOSH rating. Recommended to prevent seasonal flu and filter out larger particulate matter, but not proven to be effective. Will filter out larger particles if worn tightly. 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 still recommend these except in cases of "high risk".
NIOSH N95
One such rating is N95, which is recommended by US CDC for most cases of air contamination. These filters seal are made to seal tightly around mouth and nose and is made of material certified to block 95% of particles 0.3 μm or larger in diameter, roughly the size of a single virus and include PM2.5. [1] Nevertheless, strict protocol must be taken to wear properly these masks, even facial hair is enough to break the seal and let in particles.
NIOSH N99
A stricter rating than N95, but still not resistant to oil.
Gas mask
A gas mask may be resistant to liquids if worn properly.