Archive Notice - OSHA Archive

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

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

MAY 1 1990

Ms. Kym Mohrman
Health and Safety Officer
MAECORP Incorporated
Michigan Division
8180 Valley Point Drive
Caledonia, Michigan 49316

Dear Ms. Mohrman:

Thank you for your letter of March 23, requesting an interpretation of the Hazardous Waste Operations and Emergency Response Standard (29 CFR 1910.120).

You asked for a clarification of the following provision of this standard; (c)(4)(ii): "If positive pressure self-contained breathing apparatus is not used as part of the entry ensemble, and if respiratory protection is warranted by the potential hazards identified during the preliminary site evaluations, an escape self-contained breathing apparatus of at least five minutes duration shall be carried by employees during initial site entry."

If it is determined by sufficient information prior to site entry that respiratory protection is warranted but positive-pressure self-contained breathing apparatus is not necessary, then an escape self-contained breathing apparatus of at least 5-minutes duration must be worn by employees during initial site entry. (See also 29 CFR 1910.120(c)(5)(i) and (iii).)

While (c)(4)(ii) of the standard only applies to initial site entry, at all other times possible emergency use of respirators must be anticipated and planned for. An escape self-contained breathing apparatus may be necessary at operations performed using air purifying apparatus after initial entry is made. (See 29 CFR 1910.120(g) and 29 CFR 1910.134.)

I hope this information is helpful.


Gerard F. Scannell
Assistant Secretary