Archive Notice - OSHA Archive

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

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

November 18, 1993

Mr. Thomas J. Lukish, Director
Occupational Safety & Health Services
P.O. Box 2218
Richmond, Virginia 23217

Dear Mr. Lukish,

This is in response to your September 22 letter, requesting interpretation of the Process Safety Management (PSM) of Highly Hazardous Chemicals standard, 29 CFR 1910.119. Specifically you asked whether a threshold or greater quantity of methanol stored in an atmospheric tank and connected through a water dilution mixer by piping to a chlorine dioxide bleach liquor making process is covered by the PSM standard.

The storage of 10,000 pounds (4535.9 kg) or more of methanol, a flammable liquid, in the tank which is connected through a water dilution mixer by piping to a chlorine dioxide bleach liquor making process, as described in the enclosure to your letter, is covered by the PSM standard.

As discussed in your November 5 telecon with Mr. Rolland Stroup of my staff, additional PSM letters of interpretation issued by the Occupational Safety and Health Administration concerning the storage of flammable liquids in atmospheric tanks are enclosed for your use. 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