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 25, 1994

Mr. Robert Verb
DeVilbiss Automotive Refinishing Products
1724 Indian Wood Circle, Suite G
Maumee, Ohio 43537

Dear Mr. Verb:

Your letter of January 11, addressed to Mr. Roger Clark, former Director of the Compliance Programs Directorate of the Occupational Safety and Health Administration (OSHA) concerning the quality of compressed breathing air has been referred to the Directorate of Technical Support for response.

You requested that OSHA provide you with clarifications for the definition of an "alarm", the testing frequency of a supplied air source, the acceptability of a chemical indicator as a measuring instrument for air quality, and whether the oxygen content of breathing air should be verified.

An "alarm" is an audible device which is installed on the oil lubricated air compressor. A length of stain changing chemical gas detector tube is not considered an "alarm".

Since the breathing air system and the frequency of use vary among different users, there is no single testing frequency of air quality which will be satisfactory for all users. When a new breathing air system is installed, the air quality should be tested more frequently to establish a baseline for changing the air purification agents. Once the baseline is established, the testing frequency can be adjusted according to the service life of the air purification agents.

OSHA does not require the use of a specific instrument to verify the compliance of air quality requirements prescribed in the Compressed Gas Association Commodity Specification for Air, CGA G-7.1. Any measuring instrument which has an accuracy of ± 25% at a 95% confidence limit is acceptable.

Since the OSHA respiratory protection standard, 29 CFR 1910.134, requires that the breathing air must meet the specifications prescribed in the CGA G-7.1, and since the oxygen content in the breathing air is a requirement of the CGA G-7.1, it is imperative that oxygen content be verified in the air source.

Please feel free to contact Ching Bien at (202) 219-7065 if you have any questions.


Stephen J. Mallinger
Acting Director
Directorate of Technical Support