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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

January 11, 1996

Ms. Susan Tolley
Chevron Research and Technology Center
1003 West Cutting Boulevard
Post Office Box 4054
Richmond, California 94804-0054

Dear Ms. Tolley:

This is in response to your August 11, 1994, letter requesting interpretation of the process safety management (PSM) of highly hazardous chemicals (HHCs) standard, 29 CFR 1910.119. Please accept our apology for the delay in responding. Specifically, you requested clarification to delineate at what point a work site change would no longer be considered a modification but would be considered a new facility. Your scenario and associated questions are noted below. Our corresponding reply follows.

Scenario: Under paragraph 1910.119(i)(2)(iii), a process hazard analysis (PHA) must be performed and recommendations must be resolved or implemented before start-up of a "new facility." "Modified" facilities must meet the requirements contained in paragraph 1910.119(l) Management of change, which does not specifically require a PHA, nor does it require specific action to update or modify an original PHA. However, paragraph 1910.119(l)(2)(ii), the impact of change on safety and health, leads implicitly to consideration of how the changes will affect results of previous PHAs.

Question 1: How can we determine the point where changes to an existing facility have become so extensive that it should be considered a "new" facility? We find the PSM standard to be very clear in the definition of "replacement in kind" and how to determine the point when a facility is considered "modified", but less clear on the issue of when changes have progressed beyond "modification". For example, would the addition of a spare pump, piped in parallel with an existing pump, be considered a new facility or a modification?

Would the installation of an additional storage tank in a facility that currently handles and stores crude oil be considered a new facility, or a modification, (the flow rates and maximum inventory, but not the process in the plant, are altered)?

Question 2: When it has been determined that changes constitute a facility modification, but do not create a new facility, what is the scope of the PHA update, and how should this process be documented?

Reply: Please note under paragraph 1910.119(b), "Definitions" that a "facility" means buildings, containers and equipment which contain a process. A facility constructed on a work site where there are no other facilities is considered a new facility. Thereafter, when placed into operation, this new facility becomes an existing facility. A facility, subsequently constructed on the work site such that it is physically separated from and otherwise independent from existing facilities, is considered a new facility. (A facility is considered independent when the facility including the process(es) contained in the facility would not affect or be affected by an existing facility including the process(es) it contains. Otherwise the facility is considered a dependent facility.) Thereafter, when placed into operation, this new facility becomes an existing facility, and so on. A facility, subsequently constructed on the work site such that the facility or the process(es) it contains is connected to or otherwise dependent on an existing facility including the process(es) it contains, is considered collectively to be a modified facility. Under 1910.119(i)(1), the prestart up safety review standard would be applicable to "new facilities and to modified facilities which contain a covered process", that is, a process in which (at any one point in time) there is a threshold quantity or great amount of a HHC specified as being covered by the PSM standard.

Under paragraph 1910.119(i)(2)(iii), a PHA must be performed and recommendations resolved before start up of a new facility. Also under paragraph 1910.119(i)(2)(iii), an employer must comply with the management of change standard when existing facilities are modified more than by "replacement in kind." The pre-start up safety review standard does not specifically require an employer to conduct a PHA when a facility is modified. Under paragraph 1910.119(e)(6), a PHA must be completed initially and at least every five years thereafter. Existing facilities as of May 31, 1992, the effective date of the PSM standard, and new facilities, thereafter, are subject to the "initially completed PHA" requirement of paragraph 1910.119(e)(1). "At least every five years thereafter" is interpreted to mean that a periodic PHA may be required more frequently, for example, when an existing facility is modified more than slightly, to assure that the PHA (corresponding to the existing facility before modification) is consistent with the current process. Paragraph 1910.119(e) addresses PHA documentation requirements.

Under 1910.119(1)(1), the management of change standard would be applicable to changes to facilities that affect a covered process. The Occupational Safety and Health Administration (OSHA) did not intend that a pre-start up safety review be conducted by an employer for each facility that may be modified slightly, that is when the modification is not (emphasis added) significant enough to require a change in the process safety information (See Paragraph 1910.119(d)). Such an insignificant modification, except for "replacement in kind," would be subject to the management of change standard. This clarification is discussed in the preamble, page 6388, middle of left-hand column and page 6393, top of left-hand column, of the PSM Final Rule, a copy of which is enclosed for your use.

We appreciate your interest in employee safety and health. If we can be of further assistance, please contact the Office of General Industry Compliance, Mr. Ronald J. Davies, at (202) 219-8031, extension 110.


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