March 20, 1987

Mr. Darell A. Bevis
President
Darell Bevis Associates, Inc.
14640 Flint Lee Road, Suite D
Chantilly, Virginia 22021

Dear Mr. Bevis:

This is in response to your letter of February 24, concerning the use of loose fitting respirators by bearded individuals. We will try to answer the questions you raised in your letter concerning the protection provided by the loose fitting or helmet type powered air-purifying respirators (PAPR).

Anti-aspiration devices for the PAPRs such as the Tyvec seal or rubber side shields have been a part of the approved assembly. The wearer is required to use it to improve the protection. Our decision to accept the helmet type PAPRs as loose fitting devices as an exception to the requirement prescribed in [29 CFR 1910.134(g)(1)(i-iii)] was based on the test results conducted at the Los Alamos National Laboratory, and also on the fact that protection provided by these devices are not based on a tight seal between the face and the inlet covering of the respirator. The test results in the Lawrence Livermore National Laboratory study on PAPRs have also confirmed our decision.

There are two types of air flow requirements for the certification of continuous flow supplied air respirators (SAR) as prescribed in subpart J of [40 CFR 84]. A flow rate of four cubic feet per minute (CFM) is required for tight fitting SARs and six CFM is required for loose fitting SARs. Similar air flow rates are prescribed in Subpart K of [40 CFR 84] for tight and loose fitting PAPRs.

Any change in our position on this issue would be dependent on a critical review of the test data which you may provide.

If you have additional questions on this issue, please feel free to contact us.

Sincerely,

Edward J. Baier
Director
Directorate of Technical Support