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.

May 23, 2017


Mr. George C. Walton
1025 Executive Blvd., Ste., 101
Chesapeake, Virginia 23320

Dear Mr. Walton:

Thank you for your letter to the Occupational Safety and Health Administration (OSHA). Your letter has been referred to the Directorate of Enforcement Programs for an answer to your question. Your letter requested clarification of OSHA’s Respiratory Protection standard, which addresses qualitative and quantitative fit tests and assigned protection factors. This letter constitutes OSHA’s interpretation only of the requirements discussed herein, and may not be applicable to any questions not delineated within your original correspondence. Your paraphrased questions and our responses are below.

Question 1: When does Table 1-Assigned Protection Factors (APF) apply? After a qualitative fit test (QLFT) or quantitative fit test (QNFT)?

Response: The Assigned Protection Factor (APF)1 means the workplace level of respiratory protection that a respirator or class of respirators is expected to provide to employees when the employer implements a continuing, effective respiratory protection program. The APF for each class of respirators is established in Table 1 of the Respiratory Protection standard, 29 CFR 1910.134. Therefore, to determine the APF for a particular respirator, the employer need only look up the APF for the class of respirators to which it belongs in Table 1. Determining the APF for the respirator is necessary to evaluate whether it will adequately protect the employee against exposure to substances in the workplace air based on the concentration of those substances in the air when the employer implements an effective respiratory protection program, including fit testing. The Table 1-APFs were developed after thorough review of the available literature, including chamber-simulation studies and workplace protection factor studies, comments submitted to the record, and hearing testimony. Please see 71 FR 50122, August 24, 2006. The specific APFs listed in Table 1 are the values that rate the expected level of protection provided by different classes of respirators under ideal conditions, including a proper fit.

The fit test, required in 29 CFR 1910.134(f), is the protocol to qualitatively or quantitatively evaluate the fit of a respirator on an individual. As you correctly noted in your letter, the ‘fit factor’ estimates the fit of a particular respirator to a specific individual—it is determined by conducting the fit test of the individual with the desired respirator. An unsuccessful qualitative fit test (QLFT) or quantitative fit test (QNFT) would indicate that the respirator has not achieved a good facepiece-to-face seal for the worker being tested, and the respirator would therefore be expected to deliver less protection than the APF it was assigned in Table 1. The terms ‘fit factor’ and ‘APF’ are not interchangeable.

Please note that although a QLFT can be used to fit test all tight-fitting positive pressure respirators, a QLFT is only allowed for tight-fitting negative pressure air-purifying respirators that must meet a fit factor of 100 or less. In practice, this means that a negative pressure air-purifying respirator (APR) may be qualitatively fit tested only if the APR is to be used in workplace atmospheres where the level of the hazardous contaminant is no more than 10 times the permissible exposure limit (PEL) and lower than the level that is immediately dangerous to life or health (IDLH). For further guidance, please see The Small Entity Compliance Guide for the Respiratory Protection Standard and the Assigned Protection Factors for the Revised Respiratory Protection Standard on the OSHA website at https://www.osha.gov. If a negative pressure air purifying respirator is to be used in a workplace atmosphere where the level of the hazardous contaminant is more than ten times the PEL, a QNFT must be performed.

Please be aware that the Commonwealth of Virginia operates its own occupational safety and health program under an OSHA-approved State Plan. The Virginia Occupational Safety and Health (VOSH) Division adopts and enforces standards and investigates safety and health concerns in workplaces throughout the state. State Plans are required to have standards and an enforcement program that are “at least as effective” as OSHA’s, but may have different or additional requirements. Please contact VOSH directly at the address below, for further information and to discuss your specific compliance issue:

Virginia Department of Labor and Industry
Virginia Occupational Safety and Health (VOSH)
600 East Main Street, Suite 207
Richmond, Virginia 23219
Telephone: (804) 371-2327

Thank you for your interest in occupational safety and health. We hope you find this information helpful. OSHA’s requirements are set by statute, standards, and regulations. Our letters of interpretation do not create new or additional requirements but rather explain these requirements and how they apply to particular circumstances. This letter constitutes OSHA’s interpretation of the requirements discussed. From time to time, letters are affected when the agency updates a standard, a legal decision impacts a standard, or changes in technology affect the interpretation. To assure that you are using the correct information and guidance, please consult OSHA’s website at https://www.osha.gov. If you have further questions, please feel free to contact the Office of Health Enforcement at (202) 693-2190.



Thomas Galassi, Director
Directorate of Enforcement Programs

1 Occupational Safety and Health Administration, Assigned Protection Factors for the Revised Respiratory Protection Standard, OSHA 3352-02 2009.