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.

March 31, 1994

Ms. Doris S. Reid, Manager
Environmental Health & Safety Services
Delta Environmental Consultants, Inc.
6701 Carmel Road
Suite 200
Charlotte, N.C. 28226-3901

Dear Ms. Reid:

This is in response to your January 4, letter requesting an interpretation of the Process Safety Management (PSM) of Highly Hazardous Chemicals standard, 29 CFR 1910.119. Please accept our apology for the delay in response. When a process contains 5,000 pounds (2272.7 kilograms) or more of a 70 percent Tertiary Butyl Hydroperoxide (TBHP) and 30 percent water mixture, it is covered by the PSM standard. Mixtures of greater than 70 percent Tertiary Butyl Hydroperoxide (TBHP) and less than 30% water would also be covered.

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


H. Berrien Zettler, Deputy Director
Directorate of Compliance Programs