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Sulfuric acid and oleum under process safety management

Summary An employer asked whether sulfuric acid fell under OSHA’s process safety management rule. OSHA said 93–98 percent sulfuric acid was outside the rule and described coverage for specified concentrations of oleum, while calling the Appendix A listing erroneous; the current Appendix A still uses that listed wording.
Document
Federal opinion letter
Agency
Occupational Safety and Health Administration (OSHA)
Document number
1993-06-24-0
Date issued
June 24, 1993
Status
Archived by the agency
OSHA did not mark this letter archived, but it called the Appendix A oleum concentration listing an error and anticipated an editorial change. The current 29 CFR 1910.119 Appendix A still lists “Oleum (65% to 80% by weight; also called Fuming Sulfuric Acid),” so the discrepancy remains unresolved.
Status last verified October 9, 2026
Topics
Workplace Safety OSHA 1910 Process Safety Sulfuric Acid
Source
View the official document

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The current status of this document is unclear
OSHA did not mark this letter archived, but it called the Appendix A oleum concentration listing an error and anticipated an editorial change. The current 29 CFR 1910.119 Appendix A still lists “Oleum (65% to 80% by weight; also called Fuming Sulfuric Acid),” so the discrepancy remains unresolved. 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 Treat this page as historical context, not current guidance, and verify current law before relying on anything here.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.

June 24, 1993

Mr. Jon LaRue
Nova Engineering, Inc.
[Recipient address omitted]
Dear Mr. LaRue:

This is in response to your May 17 letter, requesting an interpretation of the Process Safety Management (PSM) of Highly Hazardous Chemicals standard, 29 CFR 1910.119. Specifically, you requested that the Occupational Safety and Health Administration clarify that sulfuric acid is not covered by the PSM standard.

Sulfuric acid, which contains 93 to 98 percent H(2)SO(4) and the remainder is water, is not covered by the PSM standard. Please note that Oleum (65-80 percent by weight, also called Fuming Sulfuric Acid), which is listed in Appendix A of the PSM standard, is in error. A workplace process which contains a threshold quantity of 1000 pounds (453.6 kg) or more of Fuming Sulfuric Acid (65% by weight or greater Sulfur Trioxide SO(3), is covered by the PSM standard. This percentage change in concentration will be the subject of editorial changes to the PSM standard anticipated in the near future.

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

Sincerely,
Roger A. Clark, Director
Directorate of Compliance Programs

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