On July 10, 1995 a new standard was issued by the National Institute for Occupational Safety and Health (NIOSH) titled 42 CFR 84.* This standard establishes new performance criteria for all negative pressure particulate air-purifying respirators and prefilters. These are widely used respirators to help protect workers from hazardous particles generated by operations such as welding, sanding, grinding, and haying.
Before this, particulate respirators were classified by NIOSH as dust/mist, dust/fume/mist, HEPA (high efficiency particulate air), etc. Under the new standard, these classes of respirators are replaced with nine new classes of air-purifying particulate filters. This is not a one to one product transition - the particulate product filter selection criteria has changed. This criteria is now based on the existence or absence of oil in the work environment**.
Filters are now classified as P Series, R Series and N Series. N Series respirators are not for use in oil environments and should be used and reused depending on hygiene considerations, damage, and increased breathing resistance. R Series respirators are oil resistant and should only be used for 8 hours of continuous or intermittent work before being discarded when the atmosphere contains oils. Finally, P Series filters are oil proof and should be used for up to 40 hours or 30 days (whichever occurs first) when oil aerosols are in the air. When used in atmospheres with non-oil aerosols, P Series filters should be used and reused depending on hygiene considerations, damage, and increased breathing resistance. Basically, if your environment does not contain oil, you can choose either N, R or P series filters. If your environment contains oil, or you are not sure, your choice is restricted to either R or P series filters.
A three year transition period to implement the new standard was over July 10, 1998. 3M Canada, in anticipation of the change has created new respirators that not only meet this new standard, but offer more in the way of comfort and breathability. For details on these products and usage recommendations please see the Choose a Respirator section.
*This summary of the respirator approval changes does not represent an official or legal, or necessarily complete, interpretation of the standard. If specific questions arise, the regulation itself should be reviewed and relied on rather than this summary.
**To determine if your workplace contains oil, consider the following definition:
Oil: Any of numerous mineral, vegetable and synthetic substances and animal and vegetable fats that are generally slippery, combustible, viscous, liquid or liquefiable at room temperatures, soluble in various organic solvents such as ether but not in water.
NIOSH standards