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.

DOL-OSHA-DEP-2020-002 - This document does not have the force and effect of law and is not meant to bind the public in any way. This document is intended only to provide clarity to the public regarding existing requirements under the law or agency policies.

September 20, 2019

Mr. Dave Worthington
403 West 21st Street
Houston, Texas 77008

Dear Mr. Worthington:

Thank you for your letter to the Occupational Safety and Health Administration’s (OSHA) Directorate of Enforcement Programs. You have requested an interpretation on requirements for updating the process hazard analysis (PHA) in OSHA’s 29 CFR 1910.119 – Process Safety Management of Highly Hazardous Chemicals. This letter constitutes OSHA’s interpretation of the requirements discussed in the letter and may not be applicable to other questions not delineated within your original correspondence.

Question: Can the “at least every 5 year” requirement for updating or revalidating Process Hazard Analyses (PHAs) in 29 CFR 1910.119(e)(6)1 be delayed and restarted again after a facility has shut down for an extended time period?


No, the requirement in 29 CFR 1910.119(e)(6) that a PHA shall be updated and revalidated at least every five (5) years following an initial PHA, as required by 29 CFR 1910.119(e)(1), cannot be delayed or applied retroactively while a plant or process unit within a chemical facility is shutdown. Since the “at least every five year” requirement of 29 CFR 1910.119(e)(6) contains no exceptions for extensions, it is therefore a fixed requirement, and the maximum time-period between the initial PHA and subsequent PHAs is dependent on the completion date of the prior PHA. For example, if the initial PHA or last PHA is completed on January 1, 2020, the next PHA update/revalidation is due no later than January 1, 2025. OSHA will not require a PHA during the period a covered process is shutdown (i.e., the system has been de-inventoried and purged of all highly hazardous chemicals (HHC)). However, if the 5-year time period expires before the next startup, the employer would be required to update and revalidate their PHA prior to introducing HHCs into the process.

Extended plant shutdowns can introduce new hazards into a process that were not previously identified, evaluated or controlled during the initial PHA. To minimize the risk of incidents prior to restart of a previously shutdown2 chemical facility, the PSM standard requires an employer to perform other activities aside from PHA revalidations including, but not limited to, the following:


  • Verify that process changes, other than replacement-in-kind, since the last PHA, undergo a documented management of change (MOC) process, as required in 29 CFR 1910.119(l).
  • Review and update process safety information in 29 CFR 1910.119(d)3 (e.g., piping and instrumentation diagrams), and operating procedures in 29 CFR 1910.119(f)4 as necessary.
  • Evaluate the adequacy of the training program to determine whether operating personnel, as well as employees engaged in both routine and non-routine work activities, necessitate refresher training5 or additional training as required in 29 CFR 1910.119(g), 29 CFR 1910.119(i)(2)(iv), and 29 CFR 1910.119(l)(3).
  • Review previous incident investigation reports and compliance audits for any recommendations that may affect the startup operation.
  • Perform a pre-startup safety review prior to introducing HHC into the modified facilities per 29 CFR 1910.119(i)(1)6 and (i)(2)7.


Thank you for your interest in occupational safety and health. We hope you find this information helpful. OSHA’s requirements are set by statute, standards, and regulations. Our letters of interpretation do not create new or additional requirements but rather explain these requirements and how they apply to particular circumstances. This letter constitutes OSHA’s interpretation of the requirements discussed. From time to time, letters are affected when the Agency updates a standard, a legal decision impacts a standard, or changes in technology affect the interpretation. To assure that you are using the correct information and guidance, please consult OSHA’s website at http://www.osha.gov. If you have further questions, please feel free to contact the Directorate of Enforcement Programs at (202) 693-2100.


Patrick J. Kapust Acting Director, Directorate of Enforcement Programs

1 29 CFR 1910.119(e)(6) At least every five (5) years after the completion of the initial process hazard analysis, the process hazard analysis shall be updated and revalidated by a team meeting the requirements in paragraph (e)(4) of this section, to assure that the process hazard analysis is consistent with the current process.

2 See 29 CFR 1910.119(i)(1) and (i)(2)

3 29 CFR 1910.119(l)(4) - If a change covered by this paragraph results in a change in the process safety information required by paragraph (d) of this section, such information shall be updated accordingly.

4 See 29 CFR 1910.119(l)(5) and 1910.119(i)(2)(ii)

5 The maximum three year operator refresher training requirement, 1910.119(g)(2), is unaffected by the time a process is shutdown.
29 CFR 1910.119(g)(2) - Refresher training. Refresher training shall be provided at least every three years, and more often if necessary, to each employee involved in operating a process to assure that the employee understands and adheres to the current operating procedures of the process. The employer, in consultation with the employees involved in operating the process, shall determine the appropriate frequency of refresher training.

6 29 CFR 1910.119(i)(1) - The employer shall perform a pre-startup safety review for new facilities and for modified facilities when the modification is significant enough to require a change in the process safety information.

7 29 CFR 1910.119(i)(2) - The pre-startup safety review shall confirm that prior to the introduction of highly hazardous chemicals to a process: