Archive Notice - OSHA Archive

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

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

September 20, 1993

Mr. David L. Smith
Constangy, Brooks & Smith
Attorneys At Law
Suite 2400
Peachtree Street, N.W.
Atlanta, Georgia 30303-1557

Dear Mr. Smith:

This is in response to your August 3 letter, requesting interpretation of the Process Safety Management (PSM) of Highly Hazardous Chemicals standard, 29 CFR 1910.119. Please accept our apology for the delay in responding. Your questions and our responses follow.

Question 1: Does an employer have to maintain records or documentation establishing the boiling points (or the 10 percent points of distillation identified in the definition of boiling point in the PSM standard) of flammable liquids stored in atmospheric tanks or transferred?

Reply: Please note that the exception at 29 CFR 1910.119(a)(1)(ii)(B) does not apply to all flammable liquids stored in atmospheric tanks or transferred which are kept below their normal boiling point without benefit of chilling or refrigeration. This exception is limited to flammable liquids in atmospheric tanks, containers and pipes used only for storage and transfer (to storage) and not connected to a process or process vessel. In response to your question, if intending to invoke the exception, an employer must be prepared to demonstrate (through documentation including records which are maintained and otherwise) to OSHA that flammable liquids stored and transferred on a work site meet this exception. In this context, an employer must disclose the boiling points of the flammable liquids intended to be excepted from PSM coverage and how the boiling points were determined.

Question 2: May an employer use the 10 percent point of a distillation (performed in accordance with the Standard Method of Test for Distillation of Petroleum ASTM D-86-62) to establish the boiling point of a flammable liquid instead of making an exhaustive attempt to establish and document an "accurate boiling point?"

Reply: Yes, the 10 percent point of a distillation may be used as noted in the 1910.119(b) definition of boiling point.

Thank you for your interest in Occupational Safety and Health. If we may be of further assistance, please contact us.


Roger A. Clark, Director
Directorate of Compliance Programs