July 1, 1997

Richard Olson, CIH
Project Manager
Environmental & Health Regulatory Affairs
The Dow Chemical Company
2030 Dow Center
Midland, MI 48674

[Dear Mr. Olson:]

This is in response to your March 27 and June 6 letters to the Occupational Safety and Health Administration (OSHA) requesting an interpretation allowing the use of a mouthbit respirator in apparent violation of [29 CFR 1910.134(d)(1)(ii)] requiring a NIOSH approved respirator during the period of an employee's escape from a chemical release of phosgene.

OSHA generally relies on the National Institute [for] Occupational Safety and Health (NIOSH) both for the requirements of the aforementioned standard and for general guidance on respiratory issues. The mouthbit respirator indicated in your letter, is approved by NIOSH for use in atmospheres containing hydrogen sulfide, chlorine, hydrogen chloride, chlorine dioxide and/or sulfur dioxide. The cartridge was specifically tested by NIOSH against each of these compounds and found to be protective. It was not, however, tested against phosgene and carries no approval for that substance. However, as a matter of policy, NIOSH recommends in its Pocket Guide to Chemical Hazards that only full-facepiece respirators be used for escape from any acid gas including phosgene due to the irritating nature of the substances, in spite of the approval given to the mouthbit respirators for other acid gases.

Your letter asserts that the mouthbit respirator can be utilized safely for protection against phosgene during an escape. You have submitted data supplied by both Scott Aviation and Cabot Safety which indicate that the respirator cartridge may be as effective a sorbent of phosgene as for the acid gases for which it is specifically approved. In addition, your letter raises a question about the real level of protection afforded by requiring a respirator which requires either more time to don or is so inconveniently bulky that most employees in areas where exposure is a remote but real possibility will choose not to wear it and instead merely exit the area of concern without any protection. And finally, all workers in the area wear chemical goggles which would inhibit the influx of gas to the eye.

OSHA agrees that use of these respirators in conjunction with chemical goggles is acceptable in cases where the employees make an immediate and unobstructed exit from an outdoor, relatively level area involved in a phosgene emergency. Such an emergency evacuation must be detected and signaled by remote or personal gas monitors which alarm at protective levels and be performed in accordance with a valid emergency action plan. The emergency action plan shall involve the employees in a training program sufficient to provide an informed judgement about the selection of respirators and ensure proper implementation of the plan. Employees should also be offered the alternative of a NIOSH approved and recommended respirator in lieu of the mouthbit respirators. OSHA will consider violations of [29 CFR 1910.134(d)(1)(ii)] requiring NIOSH approved respirators to be of a de minimis nature when these narrow set of criteria are met. This guidance would not apply to enclosed phosgene process areas, elevated workstations above two stories, or other workstation configurations which would tend to hinder [an] expeditious exit. In addition, if the frequency of phosgene releases is relatively high, [then] OSHA would expect that engineering controls be installed to reduce it or if such controls are not feasible, approved respirators be worn on a continuous basis in the affected area.

You may be aware that OSHA is currently in the process of rewriting its rule for respiratory protection, 29 CFR 1910.134. The above interpretation may have to be reconsidered in light of the requirements of the new regulation when it is published. Thank you for your interest in safety and health.

[This document was edited on 8/19/99 to strike information that no longer reflects OSHA policy.]

Sincerely,

John B. Miles, Jr., Director
Directorate of Compliance Programs

Attachment

November 14, 1997

Richard Olson, CIH
Project Manager
Environmental & Health Regulatory Affairs
The Dow Chemical Company
2030 Dow Center
Midland, MI 48674

Dear Mr. Olson:

This is in response to our telephone discussion on November 4, 1997, concerning a sentence in a previous letter the Occupational Safety and Health Administration (OSHA) sent to you on July 1, 1997. In our July letter we addressed an issue you raised about employees using a mouthbit respirator during emergencies. You stated you needed further clarification on a sentence stating "...the guidance would not apply to enclosed process areas, elevated workstations above two stories, or to other workstation configurations which would tend to hinder a expeditious exit".

Please be informed this sentence is in our July letter because the information you sent us appeared to address only lever conditions. The data you provided did not discuss such issues as worker visibility when descending elevated workstations or the potential contaminant level in enclosed process areas. As stated to you over the telephone, Dow should conduct an evaluation into what emergency respiratory device(s) would work best in various situations and document these findings.

I hope this response addresses your needs, and if you need further clarification, please contact Maureen O'Donnell at (202) 219-8036.

Sincerely

John B. Miles, Jr.
Director
Directorate of Compliance Programs