There is much confusion and misinformation about the classification and certification of respirators and face masks.
For example, lets look at N95 masks that are NIOSH Approved.
The ‘N” means it is not resistant to petroleum products and contaminants. There are two more ratings and they are R, which is somewhat resistant to petroleum and P, which is strongly resistant to petroleum.
The ’95’ means that it is designed to block 95% of particles that are 0.3 μm (microns) or bigger. For reference a single virus is usually about 3 μm.
So the N95 means it is a mask that is not resistant to petroleum products and contaminants.
NIOSH stands for “The National Institute for Occupational Safety and Health”. Here is the what they say on their website about page:
“The Occupational Safety and Health Act of 1970 established NIOSH as a research agency focused on the study of worker safety and health, and empowering employers and workers to create safe and healthy workplaces. NIOSH is part of the U.S. Centers for Disease Control and Prevention, in the U.S. Department of Health and Human Services. It has the mandate to assure “every man and woman in the Nation safe and healthful working conditions and to preserve our human resources.” NIOSH has more than 1,300 employees from a diverse set of fields including epidemiology, medicine, nursing, industrial hygiene, safety, psychology, chemistry, statistics, economics, and many branches of engineering.”
NIOSH approved means that the NIOSH organisation has approved the mask to be of a certain quality or performance. In this case, they certify that a mask meets the N95 standard.