Recirculating exhaust air in spray operations

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

November 3, 1989

Mr. Thomas J. Slavin
Manager, Health and Safety
Navistar International Transportation Corp.
[Recipient address omitted]
Dear Mr. Slavin:

This is in response to your letter of August 23, requesting an Occupational Safety and Health Administration (OSHA) interpretation on the use of recirculation of the exhaust air in spray operations in a manner that conforms to the requirements of the National Fire Protection Association (NFPA), NFPA 33-1985, Standard for Spray Application Using Flammable and Combustible Materials. You indicated in your letter that the operation you described conforms to all current NFPA standards.

Sections 5-8.1 and 5-8.2 of NFPA 33-1989 allow recirculation of exhaust air into the spray operation(s), if the exhaust air has been decontaminated to return to safe, acceptable composition, and listed equipment monitors the decontaminated exhaust air stream to signal the operator and to automatically shut down the operation in the event of a malfunction.

In the spray paint operation, you stated that the exhaust air, after being returned to the spray booth, does not increase the flammable levels of concentrations inside the booth over 6 percent of the Lower Flammable Limits (LFL), and that this is accomplished through the use of a filtering system and monitoring equipment. The 6 percent level is well below the safe levels of concentrations (below 25 percent of LFL) prescribed by NFPA.

Under the policy of de minimis violations, copy enclosed, OSHA recognizes an employer to be in compliance with the Occupational Safety and Health Act (OSH Act) if it at least complies with the applicable industry consensus standards, such as NFPA standards, and provides equivalent or greater levels of protection to employees who may be exposed to hazards. Based upon this policy and the information provided in your letter, we interpret that you provide for compliance with the OSH Act, if safe levels of concentrations are maintained within the specified operations. In operations such as maintenance activities, during which employee exposure is possible, use of positive pressure full face air respirators in compliance with 29 CFR 1910.134 is required.

If we may be of further assistance, please contact us. Thank you for your interest in safety and health.

Sincerely,
Alan C. McMillan
Acting Assistant Secretary