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.

April 14, 1993

Michael D. Zoll
Manager of Safety
Alcan Aluminum Corporation
P.O. Box 6977
Cleveland, Ohio 44101-1977

Dear Mr. Zoll:

This is in response to your February 8 letter requesting interpretations of the Process Safety Management (PSM) of Highly Hazardous Chemicals at 29 CFR 1910.119. Your questions and our responses follow. Please accept our apology for the delay in responding.

Question 1: We have annealing furnaces in several of our plants. Large coils of rolled aluminum sheet, weighing up to 30,000 pounds, are placed in large ovens. The coils are left in the ovens for several hours. The ovens are fueled by natural gas. We have propane back-up systems. Propane storage can be several thousand gallons. The process does not include any other chemicals listed in Appendix A.

Reply: The process, including the activities of storage and associated transfer, on-site movement and use of natural gas or propane, you described would not be covered by the PSM standard which excepts hydrocarbon fuels used solely for workplace consumption as fuel. (See 1910.119(a)(1)(ii)(A)).

Question 2: We have aluminum melt furnaces in several plants. These furnaces are fueled with natural gas with propane back-up as described in process 1 above. We do utilize chlorine in these processes. Gaseous chlorine is pumped into liquid aluminum to react with and remove impurities. Chlorine storage connected to the process exceeds the 1500 pounds threshold quantity listed in Appendix A. We are aware that the chlorine process is covered under the PSM standard but are not sure about the propane used as a fuel in the same process.

Reply: The furnaces and their fuel supply systems which you describe are covered by the PSM standard. They are considered part of a process containing another highly hazardous chemical, that is, 1500 pounds (3024 kgs) or more of an undiluted (industrial grade) chlorine and therefore are not excepted by 1910.119(a)(1)(ii)(A).

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