April 14, 1993

Mr. Shari Roney
Health and Safety Officer
Landlaw Environmental Services, Inc.
208 Watlington, Industrial Drive
Readsville, N.C. 27320

Dear Mr. Roney:

This is in response to your February 8 letter requesting interpretations of the Process Safety Management (PSM) of Highly Hazardous Chemicals standard, 29 CFR 1910.119. Please accept our apology for the delay in responding. Your questions and our responses follow:

Question 1: How high must the percentage of a chemical (listed in Appendix A of 1910.119) be to require compliance with the PSM standard?

Reply: The threshold quantities listed in Appendix A of the standard apply only to pure (or "chemical grade") chemicals unless otherwise specified, for example, Hydrogen Peroxide, 52% by weight or greater.

Question 2: Does Appendix A apply to compounds of the listed chemicals? If so, does the same percentage of solution apply to a compound?

Reply: Chemical compounds not listed as compounds in Appendix A are not covered by the PSM standard as toxic or reactive highly hazardous chemicals.

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

Sincerely,



Roger A. Clark, Director
Directorate of Compliance Programs