https://www.cdc.gov/coronavirus/2019-ncov/hcp/respirator-use-faq.html
The term N95 comes from the NIOSH (National Institute for Occupational Safety and Health, a body of the US government) rating where the 95 means that the material is certified to block 95% of particles 0.3 µm or larger in diameter.
NIOSH air filtration rating refers to the classification of filtration in the United States given by the National Institute for Occupational Safety and Health (NIOSH) during the certification and approval process for respiratory protective devices established under Part 84 of Title 42 of the Code of Federal Regulations (42 CFR 84). These respiratory protective devices include air-purifying respirators (APR) such as filtering facepiece respirators (dust masks) and chemical protective cartridges that have incorporated particulate filter elements.
These classifications only refer to the filtration of particles/aerosols and do not refer to the air-purifying respirator's ability to remove chemical gasses and vapors from air which is regulated under 42 CFR 84 Subpart L. For more information see Cartridge (respirator).
NIOSH has currently established nine classifications of approved particulate filtering respirators based on a combination of the respirator series and efficiency level. The first part of the filter's classification indicates the series using the letters N, R, or P to indicate the filter's resistance to filtration efficiency degradation when exposed to oil-based aerosols (e.g., lubricants, cutting fluids, glycerine, etc.).
Definitions and intended use for each series is indicated below.
The second value indicates the minimum efficiency level of the filter. When tested according to the protocol established by NIOSH each filter classification must demonstrate the minimum efficiency level indicated below.
| Respirator Class | Minimum Efficiency Level |
|---|---|
| N95, R95, P95 | 95% |
| N99, R99, P99 | 99% |
| N100, R100, P100 | 99.97% |
Standard surgical masks are primarily just intended to protect the wearer from direct splashes and sprays of blood and bodily fluid as well as the release of aerosols from the wearer that may adversely impact a patient or other individual. There are N95 versions.
https://en.wikipedia.org/wiki/NIOSH_air_filtration_rating
A hazmat suit (hazardous materials suit) is a piece of personal protective equipment that consists of an impermeable whole-body garment worn as protection against hazardous materials.