Aqueous hydrofluoric acid under process safety rules

January 28, 1994

Mr. Gerald W. Lancour, Director
Safety, Health & Environmental Affairs
McDonnell Douglas
[Recipient address omitted]
Dear Mr. Lancour:

This is in response to your letter of October 1, requesting interpretation of the Process Safety Management (PSM) of Highly Hazardous Chemicals, 29 CFR 1910.119 standard. Specifically you requested clarification as to whether the PSM standard applies to aqueous solutions of Hydrogen Fluoride.

Hydrogen fluoride and anhydrous hydrofluoric acid, both listed in Appendix A of the PSM standard, are the same highly hazardous chemical. Aqueous solutions of hydrogen fluoride, for example, 70 percent hydrofluoric acid and 30 percent water, would not be covered by the PSM standard.

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