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.

May 17, 1995

Mr. Larry D. Mattingly
Mid-Continent Company, Inc.
P.O. Box 395
Lake Monroe, Florida 32747

Dear Mr. Mattingly:

This is in response to your February 6 letter, requesting interpretation of the Process Safety Management (PSM) of Highly Hazardous Chemicals, 29 CFR 1910.119, standard. Specifically, you requested confirmation that mixing of liquefied butane, transferred by a cargo tank motor vehicle (CTMV), with gasoline stored in atmospheric tanks at terminals is not covered by the PSM Standard. Your terminal scenario and our reply follow.

Scenario: Terminal operators store gasoline in atmospheric tanks. Subsequently, this gasoline is sold over the rack to companies which sell at service stations to the general public. During the year, gasoline is shipped to the terminals by pipeline, barge, truck or rail tank car at a lower reid vapor pressure than the maximum allowed by the state or the Environmental Protection Agency (EPA), for the geographical location of the terminal. The terminal personnel test the Reid vapor pressure of the gasoline by using an instrument approved by the EPA. If the Reid vapor pressure of the gasoline is lower then the maximum allowed at the time, the terminal operator will order normal, that is, liquefied, butane delivered by CTMV(s) to raise the Reid vapor pressure of the gasoline stored in the atmospheric tanks. The normal butane is delivered to the terminal in a Department of Transportation (DOT) approved CTMV. Typically, the gasoline is pumped from an atmospheric storage tank through a pipeline where the liquefied butane is mixed with the gasoline and returned to the atmospheric storage tank. When unloaded and disconnected, the CTMV leaves the terminal operator's property. The gasoline is then retested to assure that the Reid vapor pressure is not higher than EPA regulations allow. Effective January 1, 1995, terminal operators who wish to continue normal butane blending at their terminals are required by EPA, pursuant to the Clean Air Act, to register as a refinery.

Reply: Unless additional, unaddressed circumstances require coverage, mixing of CTMV delivered butane with gasoline stored in atmospheric tanks as described in the scenario above is considered a process excepted by paragraph 1910.119(a)(1)(ii)(B) from coverage by the PSM Standard. This interpretation is based on the following factors.

1. Butane liquefied gas is delivered in compliance with DOT regulations; namely, 49 CFR Subchapter C - Hazardous Material Regulations and Particularly, Part 177 - Carriage by Public Highway.

2. In addition to the DOT regulated flammable liquefied gas, delivery activity, the process only involves atmospheric tanks storage and associated transfer.

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, Mr. Ronald J. Davies, telephone #202-219-0831, extension 110.


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