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.

March 25, 1992

Mr. Thomas G. Grumbles
Manager Environmental Affairs
Vistal Chemical Company
900 Threadneedle
Houston, Texas 77079-2990

Dear Mr. Grumbles:

This is in response to your letter of March 2, requesting a clarification on the listing of Hydrogen Chloride in Appendix A of the Process Safety Standard which was promulgated by the Occupational Safety and Health Administration (OSHA) on February 24, 1992 (57FR 6356).

Specifically, you asked why Hydrogen Chloride and Hydrochloric Acid, anhydrous were both listed in Appendix A and both had the same CAS number (CAS #7647-01-0).

The Appendix A list is referring to Hydrogen Chloride gas and its liquid form. If hydrogen chloride gas is liquefied, it is sometimes referred to as Hydrogen Chloride, Anhydrous or Hydrochloric acid, anhydrous. However, it is still the same substance. Consequently, the Agency listed the substance both ways, but with the same CAS number, to indicate that they are both the same substance.

I hope this information will be of assistance to you and have clarified your question.


Thomas H. Seymour
Deputy Director, Directorate
of Safety Standards Programs