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.

July 20, 1992

                   Regional Administrator

FROM:               PATRICIA K. CLARK, Director
                   Directorate of Compliance Programs

SUBJECT:            Aqualon Company's Request for Clarification Concerning
                   Process Safety Management (PSM) Standard,
                   29 CFR 1910.119

This is in response to your request of May 5 on this subject, regarding whether the Aqualon Company's cellulose nitrate process is covered under 29 CFR 1910.119. We concur with the Regional position on this question.

The company manufactures cellulose nitrate in a concentration greater than 12.6% nitrogen; water is then added in further processing and transfer of the material. The finished product is a mixture containing greater than 23% water, which the company indicates will not burn.

Nevertheless, as you have stated, Appendix A of the standard lists cellulose nitrate in concentrations of greater than 12.6% nitrogen as a chemical which presents a potential for a catastrophic event at or above the threshold quantity of 2500 pounds. The standard does not distinguish between "wet" or "dry" cellulose nitrate.

Therefore, if the Aqualon Company's process involves cellulose nitrate in a concentration greater than 12.6% nitrogen, with the total quantity of the mixture or solution at or above the threshold quantity--no matter what percentage of water may be used in treatment--the process is covered under the requirements of 29 CFR 1910.119.

If you have further questions on this, please contact William Smith, Division of Safety Guidance Development, at 202-523-8041.

cc: Leo Carey, Office of Field Programs