Standard Interpretations - Table of Contents Standard Interpretations - Table of Contents
• Standard Number: 1910.119(a)

April 30, 1999

MEMORANDUM FOR:    KENNETH W. GERECKE, Assistant Regional Administrator
                   Region III

FROM:              RICHARD FAIRFAX, Director
                   Directorate of Compliance Programs Assistance

SUBJECT:           PSM Applicability to a 50% Solution of Hydroxylamine

This is in response to your March 17, 1999 memorandum, to Herb Washington, Director, OSHA -- Office of General Industry Compliance on the applicability of the Process Safety Management of Highly Hazardous Chemicals; Explosives and Blasting Agents (29 CFR 1910.119) to a 50% solution of hydroxylamine.

Question 1: What is the commercial grade of hydroxylamine that would invoke coverage of the PSM standard?

Response: Highly hazardous chemicals listed in Appendix A of the PSM standard without specified concentration limits, such as hydroxylamine (CAS #7803-49-8), are intended to be covered by the PSM standard at commercial grade percentages. OSHA defines commercial grade as a typical maximum concentration of the chemical that is commercially available and shipped. The maximum concentration is an assay or nominal value which can vary ± percentages depending on the manufactures' or distributors' specifications.

The Aldrich -- Catalog Handbook of Fine Chemicals, 1998-1999, lists the maximum commercial grade concentration for hydroxylamine as a 50 weight % (50%) solution. Aldrich specifications for 50% hydroxylamine solution can vary ± 5%. Additionally, of the three known manufacturers of hydroxylamine, the maximum concentration produced is a 50% solution, therefore, it is the maximum concentration commercially available and shipped. Given the above, a 50% hydroxylamine solution is covered by the PSM standard. If a process is designed and intended to, or in fact does, contain a threshold quantity (2,500 pounds) or greater of a 50% hydroxylamine solution then the process is covered by PSM.

Question 2: A September 11, 1995 letter from John B. Miles, Director, OSHA's Directorate of Compliance Programs to Mr. Jeffery Brown, R.W. Greef & Co., Inc., states, "Assuming the commercial grade of the liquid form (hydroxylamine) is near 99% concentration, a 50% solution would not be covered by the standard." Is this a correct statement, if not, what is the maximum commercial grade concentration for hydroxylamine?

Response: OSHA has not changed its position relative to determining PSM coverage based on the maximum commercial grades of Appendix A materials. The September 11, 1995 OSHA response was technically correct because it was based on the assumption that the maximum commercial grade concentration of hydroxylamine was 99%. If that assumption were correct, a 50% solution of hydroxylamine would have been a non-covered material. In the R.W. Greef OSHA response, the "assumption" was intended to be part of an example methodology for employers to use to determine if an Appendix A material is covered by PSM based on its concentration. However, the assumed 99% maximum commercial grade concentration was not a correct value.

The maximum commercial grade concentration of hydroxylamine is, in fact, 50%. Therefore, a 50% hydroxylamine solution is covered by the PSM standard.

If you have any questions, please contact Mike Marshall in OSHA's Office of General Industry Compliance Assistance at (202) 693-1850.

Standard Interpretations - Table of Contents Standard Interpretations - Table of Contents