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.

February 5, 1996

Jeni Boyer, RRT
Clinical Education Coordinator
Respiratory Care, South Unit
St. Elizabeth Medical Center
One Medical Village Drive
Edgewood, Kentucky 41017

Dear Ms. Boyer:

This letter is in response to your request for the Occupational Safety and Health Administration's (OSHA) interpretation of respiratory protection requirements with regards to tuberculosis (TB) exposure.

Under the new respirator certification and testing guidelines issued by the National Institute of Occupational Safety and Health (NIOSH), several new categories of particulate respirators are now available on the market. These include the Type 100, the Type 99, and the Type 95. According to the NIOSH certification document, all three classes of these respirators are acceptable for use during workplace tuberculosis exposure. The Type 95 is regarded as the minimally acceptable level of respiratory protection. OSHA will still accept the use of the high efficiency particulate air (HEPA) respirator or any of these newly certified respirator classes.

There are several questions on the use of respirators that continue to be asked. These include use limitations of disposable respirators and fit testing and fit checking requirements for respirator fit. Regarding the reuse of disposable respirators, NIOSH has stated that the disposable masks can be reused for multiple uses provided the integrity of the mask has not been compromised. OSHA accepts this view. On fit checking and fit testing, our standards require that each worker assigned to wear a respirator must receive either a qualitative or quantitative fit test. Once assigned a respirator, each employee must perform a fit check of the mask every time the respirator is put on. The purpose of the fit check is to assure that the respirator is properly situated on the face and is providing a face to respirator seal comparable to when the mask was fit tested. The recommendations provided by the manufacturer for the respirator must be followed when conducting a fit check.

[This document was edited on 3/24/1999 to strike information that no longer reflects current OSHA policy.]

The last point raised in your correspondence addresses the assigned protection factor (APF) of the N-95 respirators. When a quantitative fit test is conducted, the wearer of the mask is assigned a fit factor that is based upon the APF plus a safety factor of 10. The combination of the APF and the safety factor is the derivation of the fit factor (100). OSHA has not assigned a protection factor to these masks. The agency is engaged in the rulemaking process on the respiratory protection standard. The section of the proposed standard covering APFs is currently open and under review. The agency cannot at this time state what the protection factor for these respirators would be. Nevertheless the agency will expect that for a quantitative fit test that the wearer of the respirator must achieve a fit factor of at least 100. For qualitative fit tests, the qualitative test procedure is based upon validation with a quantitative fit test method. Thus, when a properly conducted qualitative fit test has been conducted and the test individual passes the fit test, a fit factor of 100 will assume to have been achieved.

[This document was edited on 3/24/1999 to strike information that no longer reflects current OSHA policy.]

Your interest in occupational health and safety is appreciated. If you have any further questions please contact [the Office of Health Enforcement at (202) 693-2190].


John B. Miles, Jr., Director
[Directorate of Enforcement Programs]

[Corrected 10/22/2004]