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 14, 1995

Mr. J. B. Evans
Union Carbide Corporation
39 Old Ridgebury Road, K3
Danbury, Connecticut 06817-001

Dear Mr. Evans:

This is in response to your June 1, 1994 letter requesting interpretation of the Process Safety Management standard (PSM) 29 CFR 1910.119. I apologize for the delay in the response. In your letter, you describe three scenarios and questions regarding on-site natural gas in pipe lines used as a fuel and as a feed stock. The responses to the questions regarding the scenarios, as you have described them, are set forth below.

Question 1: Would the powerhouse boiler, the on-site portion of the natural gas pipe line, and the production unit furnace be considered one process, due to interconnection? If so, would the process not be a covered process because of the fuel exemption?

Reply: Hydrocarbon fuels used solely for work place consumption as fuels, and not part of a process containing another highly hazardous (covered) chemical, are not covered by the PSM standard. The natural gas system, as you have described, would not be the trigger chemical for PSM applicability. If the unit furnace contained other covered chemicals, then the furnace, pipe line and boiler could be part of the covered process to the extent they could be affected by a release of the covered material.

Question 2: If there is no fuel exemption, would the process not be a covered process because it contains less than 10,000 lbs. of flammables?

Reply: Threshold quantities of covered chemicals must be present for the PSM standard to apply. The threshold quantity for flammable gas is 10,000 lbs.

Question 3: Would the powerhouse boiler, the on-site portion of the gas pipe line and the production unit be considered one process, due to interconnection?

Reply: If the natural gas were used as a feed stock rather than a fuel in the unit furnace, the unit furnace and interconnecting pipe on-site would be a single process. The powerhouse boiler would be included if it were connected to the same on-site piping as the unit furnace. In any event, the boiler would have to be reviewed in any hazard analysis with respect to loss of this utility function and its impact on the process.

We appreciate your interest in employee safety and health. If we can be of further assistance, please contact the Office of General Industry Compliance Assistance, Ron Davies at 202-219-8031 ext. 110.


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