What should the fit factor be for chemical, biological, radiological, and nuclear (CBRN) respirators?

This question came up while hosting a fit testing training seminar with a number of first-responders earlier this week. According to OSHA full face respirators need to have a fit factor level of 500, however, some manufacturers will recommend a pass level of 2000 or 2500. A doctor in California wrote OSHA for clarification. The following was a response to that letter to OSHA about this very question:

Workers wearing full facepiece air-purifying respirators must achieve a fit factor of at least 500 when using an OSHA-accepted quantitative fit test protocol.  OSHA’s Respiratory Protection Standard, 29 CFR 1910.134, does not treat CBRN full facepiece respirators differently from other full facepiece respirators.  The standard designates an assigned protection factor (APF) of 50 for full facepiece air-purifying respirators.  The standard requires all workers who are required to wear them to be fit tested using an OSHA-accepted QNFT protocol and receive a fit factor of 500 or greater to pass.  While a manufacturer’s recommendation for a pass level of 2000 or 2500 would provide an added safety factor when fit-testing their respirators, obtaining such a fit factor does not increase the assigned protection factor for that respirator, nor does it allow the use of the respirator in a more toxic atmosphere.  When enforcing this standard, OSHA would still require that these tight-fitting full facepiece respirators achieve the minimum pass level of 500 when using QNFT as provided in paragraph 1910.134(f)(7). OSHA also would allow a manufacturer’s higher pass level to be used.

So a fit factor of 500 for CBRN respirators is needed to be compliant with OSHA. If a department or agency wishes to require a higher fit factor level, that is allowed, but not required.

For the full response from OSHA.

Our training focused on using the TSI Portacount for quantitative respirator fit testing.

RAECO-LIC LLC is the authorized TSI representative  in the Midwest United States.

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  1. #1 by Keith Mullen on September 4, 2014 - 1:28 pm

    Just for added information: The USAF does QNFT to all air force personnel with their CBRN (chemical, biological, radiological, and nuclear) masks (gas masks). The fit factor that the Air Force uses is 2000. This is excerpted from their AFI Standard 48-137:

    “The Air Force selected a FF of 2000 as a division between “adequate” and “poor” fitting gas masks. The FF indicates how well the mask fits; it is not a protection factor (PF). A PF indicates the degree to which an adequately fitted mask will reduce the concentration of a contaminant.

    For a given contaminant, an adequately fitted mask with a protection factor of 10,000 will reduce the wearer’s exposure to 1/ 10,000th of the contaminant level outside the mask. The QNFT does not measure the protection factor. It is also important to realize that the Air Force masks were not designed to fit 100 percent of the Air Force population; there will be persons who, due to the size and shape of their heads, will fall outside the design percentiles for the mask.

    Currently there is no capability to make custom masks.”

  2. #2 by raecotom on September 4, 2014 - 4:23 pm

    Thanks for the info Keith!

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