OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.


March 18, 1996

Kenneth V. Vaughan, President
Neoterik Health Technologies, Inc.
Neoterik Center, Box 128
Woodsboro, MD 21798

Dear Mr. Vaughan:

This is in reply to your letter, dated March 7, 1996, concerning the relationship between OSHA standards and the usage of particulate respirators certified under 42 CFR 84. Specifically, you requested clarification concerning the requirement in the OSHA asbestos standards to use a HEPA filter respirator if concentrations do not exceed 1 fiber/cc.

It is OSHA policy that when any OSHA standard requires the use of HEPA filters then the employer may satisfy the requirement by choosing to use a P100, N100, or R100 filter certified under 42 CFR Part 84, since such filters would exhibit minimum leakage. The employer would be expected to choose either the P-, N-, or R-filter based on the environmental conditions under which the respirator would be worn.

Please contact this office if we can be of further assistance.


Kenneth W. Gerecke
Assistant Regional Administrator

[Corrected 10/22/2004]


March 7, 1996

U.S. Department of Labor-OSHA
Gateway Building, Suite 2100
3535 Market Street
Philadelphia, PA 19104


Will you please help me to understand the relationship between OSHA regulations and the use of particulate respirators certified under 42 CFR 84.

To illustrate my difficulty, I'd like to refer to the Asbestos Standard 29 CFR 1910.1001. This standard states that when the airborne concentration of asbestos is not in excess of 10 times the PEL, the required respirator is a half mask air purifying respirator equipped with high efficiency (HEPA) filters.

In Appendix B, on pages 13 and 14, of the NIOSH guide to the Selection and Use of Particulate Respirators Certified Under 42 CFR 84 (copy attached for your reference), there are presented selection guidelines for the substitution of Part 84 respirators for Part 11 respirators already in use. This explains how to select a part 84 filter if you are currently using a HEPA filter, and states that an N100 or a R100 or a P100 filter are acceptable. Also, in the second paragraph of the same Appendix B, it states that there may be situations where the 99% or the 95% filters can substitute for HEPA filters.

I would like you to clarify for me the OSHA requirement to use HEPA filters against asbestos if the concentration does not exceed 10 times the PEL. Does this requirement still exist, or has it been replaced by the NIOSH selection guidelines?

The filter classified as a P100 in Part 84 is the only Part 84 filter that is, in all senses, a HEPA filter as required by 1910.1001, the asbestos standard. Is it OSHA policy that when a current OSHA standard specifies the use of a respirator with a HEPA filter, that the only Part 84 filter that will be accepted by OSHA is the P100 filter? Or, alternatively, is it OSHA policy to permit the use of Part 84 filters such as N100, or N99 or N95 filters for use against asbestos?

My question, of course, concerns all those OSHA standards where HEPA filters are specified, not only the asbestos standard. So, in addition to the specific asbestos questions above, can you tell me if it is OSHA policy to allow the P100 filter as the only substitute for HEPA filters, when HEPA filters are required by an OSHA standard.


Kenneth V. Vaughan