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.

October 28, 1992

Ms. Allison M. Schieli
Support Services Administrator
EBASCO Services Incorporated
Two World Trade Center
New York, New York 10048-0752

Dear Ms. Schieli:

This is in response to your August 13 letter, regarding interpretation of the Final Rule on Process Safety Management (PSM) of Highly Hazardous Chemicals published in Volume 57, Number 36, of the Federal Register on Monday, February 24, 1992. You asked for clarification of paragraph 1910.119(e)(6) of the PSM Standard which requires updating and revalidating the initial process hazard analysis (PHA) required by 1910.119(e)(1). Your questions and our responses follow. As a result of the September 17 telephone communication between you and Mr. Ronald Davies of my staff, these questions replace those posed in your letter.

    Question 1:    If a natural gas company has five sites with
                   facilities performing the same process, does
                   a separate PHA need to be performed for each
                   site, for each facility at these sites or for
                   each process at each facility?

Reply: The PSM Standard is applicable, on a site by site basis, to each worksite, which has one or more facilities containing one or more processes involving one or more of the covered highly hazardous chemicals. A worksite may be simply one facility containing a single process. (See the definition of "facility" in Subsection (b) of 1910.119). On the other hand, a worksite may be a complex of facilities, each containing one or more processes. By paragraph 1910.119(e)(1), employers are required to perform initial PHA's on processes involving highly hazardous chemicals covered by the PSM Standard. An employer may use a generic hazard analysis approach for the same (or nearly the same) covered process at an individual worksite. The employer must account for variations (differences in siting, incident histories, technology, equipment, operations, etc.) for each process covered by this generic approach. Generic process hazard analysis is addressed in section 4. of nonmandatory Appendix C, Compliance Guidelines and Recommendation for Process Safety Management, to section 1910.119.

    Question 2:    What is the time frame for completion of the
                   initial PHA's and for updating and
                   revalidating them?

Reply: By paragraph 1910.119(e)(1), all initial PHA's must be completed as soon as possible, with at least 25 percent of them completed by May 26, 1994, 50 percent by May 26, 1995, 75 percent by May 26, 1996 and all completed by May 26, 1997. Initial PHA's must be updated and revalidated at least every 5 years thereafter (see paragraph 1910.119(e)(6). When employers update and revalidate a PHA before the 5 year deadline, the subsequent update and revalidation must be completed within the next 5 year period.

Thank you for your interest in occupational safety and health. If we maybe of further assistance please contact us.


Roger Clark,
Directorate of Compliance Programs