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 3, 1993

Mr. John E. Lee III
Director of Safety and Health
National Oats Company
1515 H. Avenue, N.E.
Cedar Rapids, Iowa 52402

Dear Mr. Lee:

This is in further response to your January 29 letter to Ms. Janice Barrier, Assistant Regional Administrator for Technical Support in the Kansas City Regional Office of the Occupational Safety and Health Administration (OSHA). Your letter was forwarded through Mr. John T. Phillips, Kansas City Regional Administrator to the Directorate of Compliance Programs for response. In your letter you requested that OSHA clarify whether certain fumigants used to control insects in food plants are covered by the Process Safety Management (PSM) of Highly Hazardous Chemicals standard at 1910.119.

A workplace fumigation process which contains a threshold quantity, that is, 2500 pounds (1,134 kgs) or greater amounts of methyl bromide is covered by the PSM standard. Also, a workplace fumigation process containing a threshold quantity, that is, 100 pounds (45.6 kgs), or greater amounts of phosphine (hydrogen phosphide) generated in a workplace facility at any one time by the following chemical reactions identified in your letter are covered by the PSM standard.

AlP + 3H(2)O -> Al(OH)(3) + PH(3) Mg(3)P(2)+6H(2) -> 3Mg(OH)(2) + 2PH(3)

Where: AlP is aluminum phosphide Mg(3)P(2) is magnesium phosphide H(2)O is water Al(OH)(3) is aluminum hydroxide Mg(OH)(2) is magnesium hydroxide Ph(3) is phosphine (hydrogen phosphide)

The analysis for this clarification follows. The definition of process includes the activities of storage and use of covered highly hazardous chemicals. Also, facility is defined as a building, container or equipment which contains a process.

From a storage standpoint, the 1910.119 standard would not apply to an employer who segregates his inventory by dispersing storage of highly hazardous chemicals, such as methyl bromide in amounts which do not exceed the threshold quantity so that a release from one storage area would not contribute to or cause a release from others around the workplace.

Thank you for your interest in occupational safety and health. If we can be of further assistance, please contact us.


Roger A. Clark, Director
Directorate of Compliance Programs