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.

January 15, 1999

Mr. Cass Willard
Paradigm Consulting Group
77 E. Fox Run Circle
Jenks, OK 74037-9504

Dear Mr. Willard:

This is in response to your letter dated September 2, addressed to Mr. John Miles, the former Director of the Occupational Safety and Health Administration's (OSHA's) Directorate of Compliance Programs. You requested clarification of the fit testing requirements of the new Respiratory Protection Standard, 29 CFR 1910.134.

In your letter you ask for a statement of clarification regarding when to use either quantitative or qualitative fit testing.

Qualitative Fit-Testing (QLFT) may be used to fit test negative pressure air-purifying respirators, if they will only be used in atmospheres less than ten times the PEL, since existing evidence only validates the QLFT protocols listed in Appendix A to identify respirators that achieve a fit factor of 100.

For greater concentrations, quantitative fit-testing (QNFT) must be used. When quantitative fit-testing is used, all full-facepiece respirators must meet or exceed a fit factor of 500, while quarter- and half- mask respirators must meet or exceed 100.

For all positive pressure, atmosphere-supplying respirators, either qualitative or quantitative fit testing may be used. While atmosphere-supplying respirators are fit-tested in the negative pressure mode, these respirators are most often used as positive pressure respirators in the workplace. Positive pressure atmosphere-supplying respirators that pass the QLFT or QNFT fit test may be used at the higher protection factors assigned these respirators. Both methods will detect most leakage and identify poorly fitting respirators. Any minor leaks should be overcome by the positive pressure present under normal use.

OSHA's policies and procedures for compliance with the Respiratory Protection Standard are published in the compliance instruction CPL 2-0.120, "Inspection Procedures for the Respiratory Protection Standard." This OSHA Instruction is available through the Internet on OSHA's Home Page located at the following address: http://www.osha.gov. In addition, on August 3, 1998, OSHA published Questions and Answers on the Respiratory Protection Standard. This 79 page document contains guidance regarding the Respiratory Protection Standard. This can be found on the Internet at the OSHA Home Page as well.

Should you require any additional information on this matter, please contact OSHA's Office of Health Compliance Assistance (OHCA) at 202-693-2190.


Richard E. Fairfax
Directorate of Compliance Programs