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.

August 13, 1999

Major Ellen England
2513 Kennedy Circle
Brooks AFB TX 78235

Dear Major England:

Thank you for your June 3, 1999 letter to the Occupational Safety and Health Administration's (OSHA's) Directorate of Compliance Programs (DCP). You have a question regarding portable breathing air compressors that are used to supply breathing air to a respirator. You specifically ask if an employer is required to collect samples of the breathing air generated from a portable breathing air compressor, or an electric compressor, to ensure that the compressed breathing air meets at least the requirements for Grade D breathing air.

No, the provisions in paragraph (i) in 29 CFR 1910.134, Respiratory Protection, do not apply to portable breathing air compressors (sometimes referred to as ambient air movers or free air pumps). The main concern with a portable breathing air compressor is the proper placement of the compressor. The employer must choose a location where the compressor will draw only clean breathing air from the surrounding environment. Furthermore, the standard requires employers to ensure that carbon monoxide levels in the breathing air do not exceed 10 ppm. With regard to portable breathing air compressors, the employer must measure carbon monoxide levels each time the compressor is moved to a new location.

Thank you for your interest in occupational safety and health. For your information, the original standard, 29 CFR 1910.134, OSHA Instruction CPL 2-0.120, and other materials are available on OSHA's Internet website, http://www.osha.gov. We hope this information is helpful. If you have any further questions, please feel free to call OSHA's Office of Health Compliance Assistance at (202) 693-2190.


Richard E. Fairfax, Director
Directorate of Compliance Programs