N95 masks are air purifying facepiece respirators that cover the lower half of the face and protect the wearer from inhalation of small non oil particles, although not from inhalation of gases or fumes. They are subject to performance standards stipulated by the United States NIOSH. The NIOSH (National Institute for Occupational Safety & Health) is responsible for producing performance standards for industrial equipment that help to ensure worker safety.
NIOSH standards require N95 masks to demonstrate the ability to filer at least 95% of small (0.3 micron sized) particles. They must also demonstrate that their air inhalation and exhalation flow resistance levels do not exceed certain levels. This helps to ensure the the wearer will be able to continue breathing while wearing the N95 masks, but without too much difficulty.
Other NIOSH requirements applicable to masks seeking the N95 certification include being fitted with adjustable nasal splints. the intention here is to ensure that the user will be able to adjust the masks to achieve an airtight seal between its edges and his/her facial contours.
The NIOSH does not explicitly require any specific type of harnessing mechanism for an N95 mask. However, they have indicated a preference for the head strap mechanism. As a result, the use of earloops among these masks is very rare. The overwhelming majority use headstraps instead.
The NIOSH has also formulated standards for the performance of exhalation valves fitted to N95 masks. However, the masks in this section do not include such valves. As a result, we will not mention those performance standards here.