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.

September 11, 1995

Richard H. LaLumondier
Technical Director, ILTA
1133 15th Street, N.W., Suite 650
Washington, D.C. 20005

Dear Mr. LaLumondier:

This letter is to confirm the phone conversation between yourself and Mr. Ron Davies of my staff regarding storage of flammable liquids and the applicability to the Process Safety Management standard (PSM), 29 CFR 1910.119. The discussion concerned elected rather than required refrigeration of flammable liquids in storage and the exception at 29 CFR 1910.119(a)(1)(ii)(B).

The PSM standard applies to those processes, with certain exceptions, that contain 10,000 pounds of flammable liquids. The process you describe appears to meet the exception regarding storage and transfer of flammable liquids in atmospheric storage tanks, as defined, that are kept below their normal boiling point without the benefit of chilling or refrigeration. The chemicals described do not require refrigeration to stay below their normal boiling points. The fact that an employer elects to refrigerate the chemical does not negate the exception.

Many refrigeration systems use ammonia as the cooling medium. The PSM standard applies to ammonia in refrigeration systems containing 10,000 pounds or more. Whereas the chemicals may be excepted by the storage and transfer exception, they may be covered as part of a covered refrigeration process using ammonia in excess of the threshold quantity.

Thank you for your interest in occupational safety and health. If we can be of further assistance, please do not hesitate to contact Ron Davies at (202)219-8041.


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