Classes of NIOSH-Approved Respirator Filters

The filters used in respirators must be NIOSH approved. NIOSH recognizes nine filter types that are approved for non-powered air-purifying respirators. NIOSH designates a two-part classification for filters. The first part of the classification is based on three levels of resistance to degradation by oil and it is identified by a letter, as follows:

• "N" which indicates that filters are not resistant to oil
• "R" which indicates that filters are somewhat resistant to oil
• "P" which indicates that filters are strongly resistant to oil, or oil-proof

The second part of the filter classification is based on three levels of filter efficiency and it is identified by a number, as follows:

• 95, which indicates that at least 95% of airborne particles are filtered out
• 99, which indicates that at least 99% of airborne particles are filtered out
• 100, which indicates that at least 99.97% of airborne particles are filtered out

Using this classification system, for example, an "N95 respirator" is a filtering facepiece air-purifying respirator that filters at least 95% of airborne particles but is not resistant to oil. A "surgical N95 respirator" is an N95 respirator that has an extended border made of surgical mask material to prevent splashes from coming in contact with the wearer.

To learn more about Healthcare Respiratory Protection visit our Cal/OSHA Healthcare Respiratory Protection Safety Online Training web page.