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.

April 24, 1986

Mr. G.T. Slay
Martin Marietta Energy Systems, Inc.
Post Office Box P
Oak Ridge, Tennessee 37831

Dear Mr. Slay:

This is in response to your letter of March 12, concerning air line couplings used in a supplied air respirator (SAR) system.

The Occupational Safety and Health Administration (OSHA) respiratory protection standard states that "Air line couplings shall be incompatible with outlets for other gas systems to prevent inadvertent service of air line respirators with nonrespirable gases or oxygen,"     (Correction 11/24/98) ["The employer shall ensure that breathing air couplings are incompatible with outlets for nonrespirable worksite air or other gas systems. No asphyxiating substance shall be introduced into breathing air lines,"] 29 CFR 1910.134[(i)(8)]. The intent of this standard is to prevent the inhalation of gases other than breathing air by the SAR wearer. If there is a likelihood that the breathing air may be contaminated or replaced with toxic gases, a separate air line for transporting breathing air is required.

There would be a violation of the standard if the breathing air and other toxic gases are transported through with the same system.

We hope we have addressed your concern.


Edward J. Baier
Directorate of Technical Support