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.

January 29, 1992

Mr. George L. Notarianni
Logan Associates, Inc.
Post Office Box 115
Farmington, Michigan 48332

Dear Mr. Notarianni:

This is in response to your request for an interpretation regarding respiratory protection requirements under the Occupational Safety and Health Administration's (OSHA) Ethylene Oxide (EtO) standard. Your letter of September 19, to Mr. William Q. Wiehrdt, Assistant Regional Administrator for Technical Support in our Chicago Regional Office, was forwarded to us. We apologize for the long delay of this response.

You specifically requested clarification of OSHA's position with regard to the requirements of 29 CFR 1910.1047(g) which requires respiratory protection to be used "in work operations, such as maintenance and repair activities, vessel cleaning, or other activities for which engineering and work practice controls are not feasible." Section (f)(1)(iii) of 1910.1047 specifically lists the "changing of ethylene oxide tanks on sterilizers" as an operation for which engineering controls are "generally infeasible."

The requirement for respiratory protection to be worn during tank changing operations is a precautionary measure which may provide adequate protection to employees from high or peak exposures that have the potential to occur quickly and without warning during this potentially hazardous procedure. As illustrated by the example of an ethylene oxide leak which occurred during tank changing operations in a Michigan hospital (given as an attachment to your letter), the potential for worker exposure to a high level of ethylene oxide definitely exists during such operations. The requirement for employees who change these tanks to be provided with and to wear appropriate respiratory protection would protect them from a high, unexpected release, a reasonably predictable occurrence given the nature of this operation.

With regard to this interpretation, questions have arisen regarding the OSHA policy that lack of respiratory protection is not a citeable violation unless or until the permissible exposure limit (PEL) is exceeded.

While this is OSHA's general policy for occupational overexposures to airborne concentrations of hazardous substances regulated under the 1910.1000 "Z" Tables' PELs, occupational exposure to ethylene oxide is regulated by the more specific 1910.1047 Ethylene Oxide standard. The EtO standard's substance specific requirements take precedence over the Agency's more general policies applicable to occupational exposure to other airborne contaminants. The requirement for respiratory protection during tank changing operations is specifically addressed in the EtO rule, and exposure monitoring data demonstrating overexposure to the EtO PELs need not be established before the requirement to wear respirators during these operations is effective.

The intent of the requirement at 1910.1047(g), to prevent exposure from a situation where potentially high, unexpected exposures could occur, could alternatively be met by providing real-time, continuous exposure monitoring (instantaneous readout), of the area where the EtO tanks are maintained. Such monitors would, additionally, need to be triggered to an emergency alarm for employee evacuation of the area in the event of a leak or sudden release of EtO. In the event of such an emergency, employers must assure that the emergency procedures required under 1910.1047(h) are followed.

The implementation of these procedures could provide equivalent protection to employees and, although still a technical violation of the standard, their use in lieu of the currently-required respirator use would bear no direct or immediate relationship to employee safety and health. In these instances, any violation of the specific requirements of 1910.1047(g) may be considered as "de minimis" if adequately demonstrated by the employer as providing equivalent employee protection.

We hope this has been responsive to the concerns you raised. A copy of this letter will be transmitted to OSHA's Regional Administrators for their information and reference during future enforcement efforts under the Ethylene Oxide standard.

Please feel free to contact us again if we can be of further assistance.


Patricia K. Clark, Director
Directorate Compliance Programs