Ezel / Labor Guidance / US
Back to Federal guidance

Process safety threshold for listed chemicals and compounds

Summary An environmental services firm asked when listed chemicals and compounds trigger process safety management. OSHA said Appendix A thresholds applied to pure listed chemicals unless the entry specified otherwise, and compounds not listed as such were not covered as toxic or reactive chemicals under that list.
Document
Federal opinion letter
Agency
Occupational Safety and Health Administration (OSHA)
Document number
1993-04-14-3
Date issued
April 14, 1993
Status
Archived by the agency
OSHA labels this an archive document and warns that it may no longer represent current policy.
Status last verified October 9, 2026
Topics
Workplace Safety OSHA 1910 Process Safety
Source
View the official document

Apply this to your situation

This page explains the general guidance. Ask about your specific situation and see what current federal labor law says, with citations.

The current status of this document is unclear
OSHA labels this an archive document and warns that it may no longer represent current policy. It may no longer reflect the agency's current position. Treat this page as historical context, not current guidance, and verify current law before relying on anything here.
About this page: The full text below is the official document from Occupational Safety and Health Administration (OSHA). Ezel adds the plain-English summary and tracks the document's status. The official source linked on this page is authoritative for any reliance.

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

April 14, 1993

Mr. Shari Roney
Health and Safety Officer
Landlaw Environmental Services, Inc.
[Recipient address omitted]
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

Related guidance

Permanently labeled locks for electrical lockout Opinion Letter · August 17, 2026 Helmet selection for lateral head-impact hazards Opinion Letter · August 17, 2026 Asbestos precautions when restoring drywall after flood damage Opinion Letter · May 7, 2026 Enforcement policy for recording and reporting COVID-19 cases Guidance · March 31, 2026

What does federal law require in your situation?

Ezel checks current federal labor law against your facts and answers with citations.

Opens in Ezel Pro.

  • Checks the law as it stands today, not only this page
  • Cites every source it relies on, so you can verify it
  • Chat, drafting and research in one workspace