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.


This letter constitutes OSHA's interpretation only of the requirements discussed and may not be applicable to any situation not delineated within the original correspondence.


July 9, 1999

Mr. Joe Virsack
2990 Persimmon Dr.
York, PA 17404

Dear Mr. Virsack:

Thank you for your January 27, 1999 letter to the Occupational Safety and Health Administration's (OSHA's) Directorate of Compliance Programs (DCP). You have questions regarding the application of OSHA's Process Safety Management of Highly Hazardous Chemicals; Explosives and Blasting Agents (PSM) standard (29 CFR 1910.119) to a particular situation. Your specific question deals with the applicability of the PSM standard to a manufacturing site containing flammable liquids. We apologize for the delay in our response.

Question: Does the PSM standard apply to a site with the following materials and configuration?


  • Flammable liquids are stored on-site in 5-gallon containers;
  • The combined total of flammable liquids in containers on-site exceeds 10,000 pounds;
  • The flammable liquids are stored in two separate on-site locations approximately 1,000 feet apart; and
  • The flammable liquids are used in a manufacturing process.



Reply: As no information was provided about the quantity of highly hazardous chemicals (HHC), e.g., flammable liquids, in the manufacturing process, we cannot evaluate PSM coverage for the site you described. However, utilizing your information and the assumed process configurations we offer the following:

The flammable liquid manufacturing process in question would be covered if any of the following conditions exist:



  1. The flammable liquid manufacturing process, excluding quantities in storage, contains 10,000 pounds or more of a flammable liquid; or
  2. The flammable liquid manufacturing process does not itself contain a threshold quantity of an HHC, but is interconnected or is proximate to a PSM-covered process such that:
    1. the flammable liquid manufacturing process could cause a release from the PSM-covered process by means such as fire, explosion, inadvertent mixing of incompatible chemicals, deviation, upset, etc.; or
    2. the flammable liquid manufacturing process could interfere with the mitigation of a release of an (HHC).



Based on the 29 CFR 1910.119(a)(1)(ii)(B) exception for the storage of flammable liquids in atmospheric tanks, PSM does not apply to the container storage of flammable liquids as described above. (See OSHA's website: http://www.osha.gov [interpretation link] for the interpretation letter to Mr. Joseph G. Gerard, dated June 4, 1992.) However, if the facility contains a PSM-covered process, the process hazard analysis, required by 1910.119(e), must include information regarding any hazards (e.g., fire, explosion, etc.) related to the flammable liquid storage areas which might affect a release of an HHC from a PSM-covered process or interfere with the mitigation of a release of an HHC.

Thank you for your interest in occupational safety and health. We hope you find this information helpful. Please be aware that OSHA's enforcement guidance is subject to periodic review and clarification, amplification, or correction. Such guidance could also be affected by subsequent rulemaking. In the future, should you wish to verify that the guidance provided herein remains current, you may consult OSHA's web-site at http://www.osha.gov. If you have any further questions, please feel free to contact [the OSHA Office of General Industry Enforcement at (202) 693-1850].


Richard Fairfax, Director
Directorate of Compliance Programs

[Corrected 6/21/07]