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 27, 1994

Mr. Bobby J. Sasser
Director of Corporate Safety
Reynolds Metals Company
P.O. Box 27003
Richmond, Virginia 23261-7003

Dear Mr. Sasser:

This is in response to your April 12 letter, requesting interpretation of the Process Safety Management (PSM) of Highly Hazardous Chemicals standard, 29 CFR 1910.119. Specifically, you requested clarification on whether flammable liquids used to mix (1) inks used in printing on aluminum foil and paper and (2) paint used in coating aluminum sheets as described in the scenario below are covered by the PSM standard. Please accept our apology for the delay in responding.


Flammable liquids are stored in a tank room at atmospheric temperature and pressure in eleven separate tanks, each having a capacity of over 10,000 pounds of flammable liquid. Flammable liquids are transferred to the ink room through rigid piping by pumps. The liquids are dispensed into small portable containers in the ink room, through appropriate valves and meters, where they are mixed to produce printing inks.

One liquid, ethyl acetate (flash point 24 degrees F, and boiling point 171 degrees F), can also be discharged into either of three separate 300 gallon (2,200 pounds) mixing tanks in the ink room. The mixing tanks are filled through rigid piping discharging over the top of the tank. There is no direct connection between the mixing tanks in the ink room and the storage tanks in the tank room. If all three mixing tanks are filled simultaneously, the total quantity would be less than 10,000 pounds. Contents of the mixing tanks are dispensed into smaller, portable containers for manual transfer to the printing presses. Five gallon pails and fifty-five gallon drums of flammable liquids, mixed ink room. These materials are dispensed into smaller containers for mixing purposes and/or manually transferred to the printing presses.

The above scenario would be covered by the PSM standard. By the definition of "process", the eleven flammable liquid storage tanks in the interior tank room and the three mixing tanks and other 5 gallon and 55 gallon flammable liquid containers in the adjacent ink room would be considered a single process. Please note that for the purpose of determining whether there is a threshold quantity of greater amount at any one point in time, flammable liquids contained in the process are considered aggregate.

These tanks and containers are connected by piping or unconnected and in close proximity to each other such that collectively, the flammable liquids in these tanks and containers could be involved in a potential release. See the preamble discussion in the middle column of page 6372 of the PSM Final Rule (copy enclosed) for further clarification of the basis for this provision of the standard.

Please note that the term "interconnected" includes on-site movement of flammable liquids from storage tanks by way of rigid piping which is not directly connected to but dispenses by way of a control valve directly into the mixing tanks as described in your letter. Mixing within the ink room cancels the exception at 1910.119(a)(ii)(B) which allows only storage and associated transfer as excepted activities.

We appreciate your interest in occupational safety and health. If we can be of further assistance, please contact the Office of General Industry Compliance Assistance, Ronald Davies on 202-219-8031 extension 110.


Raymond E. Donnelly, Director
Office of General Industry
Compliance Assistance