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.

September 4, 1996

Charles E. Martin, President
Modern Safety Techniques
Post Office Box 87 11388 Breiniger Road
Hicksville, Ohio 43526

Dear Mr. Martin:

This is in response to your letter of March 8, regarding your belt mounted filtration unit to be used with any National Institute for Occupational Safety and Health (NIOSH) approved supplied-air respirator. You are seeking Occupational Safety and Health Administration (OSHA) acceptance of this device to further assure Grade D air that is delivered by a compressor, by allowing the interruption of an approved respirator system to insert your belt-mounted system.

As you are probably aware NIOSH does not evaluate or approve belt mounted filtration systems that incorporate a discharge port to supply process air. Because of safety and health concerns over backflow, contamination of the respirable airstream, pressure loss, and airflow regulation, NIOSH does not approve any supplied-air respirators for use with any device that allows pneumatic tools to be operated from the respirable air stream. Due to the above listed concerns OSHA supports NIOSH. Furthermore, the current NIOSH regulations (42 CFR Part 84.141) require that Grade D or higher quality air be supplied to be supplied-air respirator at the point where the NIOSH approved air supply hose connects to the respirable air source.

All new respiratory protection devices, such as your belt mounted breathing air purifier, as well as associated devices with the air purifier (e.g., hoses, hoods, helmets, etc.), must be approved by NIOSH for compliance with respiratory protection requirements as set forth by that Agency. We encourage you to continue working with NIOSH.

Thank you for your interest in occupational safety and health. If we can be of further service, please contact us.


Ruth McCully, Director
Office of Health Compliance Assistance