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 http://www.osha.gov.

February 8, 2016

Mr. Richard F. Graham
MSA North America
116 Broadwater
Williamsburg, Virginia 23188

Dear Mr. Graham:

This is in response to our meeting on July 23, 2015, and your follow-up letter dated July 24, 2015, regarding the fit testing requirements in OSHA’s Respiratory Protection standard, 29 CFR 1910.134.  In the meeting and letter you specifically ask for clarification on whether employees need to be fit-tested twice if they are required to use a different head harness for the same model facepiece. This letter constitutes OSHA's interpretation only of the requirements discussed and may not be applicable to any question not delineated within your original correspondence. Your situation is summarized below and your paraphrased question is followed by our response.

Background: You’ve pointed out that in some workplaces, employees may be required to wear a different harness on the same manufacturer’s model facepiece and sealing surface for different work scenarios such as different work modes (negative vs. positive pressure) or for flame and heat protection. During our meeting, we discussed, in particular, a few of MSA’s respirators that use different harnesses on the same model respirator. One respirator model has two harness options that connect to the same attachment points on the facepiece and adjust in the same manner but are made of different material (i.e., rubber or Kevlar®). Another model has either a five-point or a four-point head harness option, but the facepiece only has four attachment points.

Question: Does OSHA’s Respiratory Protection standard require a separate fit test for each harness where respirator wearers are required to use different harnesses, depending on their job task?

Response: The Respiratory Protection standard requires employees to be fit tested prior to the initial use of a respirator, and whenever a different respirator facepiece (size, style, model or make) is used. See 29 CFR 1910.134(f)(2). Many respirator manufacturers have product lines offering a number of different models, but having the same elastomeric face seal. Different models can have different variations in harnesses and features on the body of the respirator facepiece, such as dual inhalation ports verses a single inhalation port, or mask composition (e.g., neoprene, silicone, or rubber). These variations can all affect respirator fit, and therefore require separate fit tests.

Each respirator model needs to be fit tested separately for each different harness. The harness and facepiece configuration used during the job task must be the same type as used during the fit test. Harness material of different composition or configurations (e.g., buckles with pull-through straps compared to belt-type straps) may be dissimilar in ways such as the length, thickness, and cross sectional area, that may impact the forces used to create the needed pressure in the face seal area. Some straps require low strap tension to create enough pressure to get an adequate fit factor, while other strap material with the same tension may create too much pressure, thereby actually inducing leakage. Also, attaching a five-point head harness on a facepiece that only has four attachment points would require the facepiece to be donned and doffed differently from the four-point head harness that was used in the fit test.

The strap type is important during training and the fit test because the user must determine the level of tightness that the head harness requires to provide the best seal and most secure fit.  This is not possible if only one type of harness is used during the fit test but others are used in the job task.

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 http://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