OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.

December 30, 1993

Mr. G. W. Lancour, Director
Safety, Health and Environmental Affairs - MDC
McDonnell Douglas Corporation
P.O. Box 516
St. Louis, MO 63166-0516

Dear Mr. Lancour:

The purpose of this letter is to further clarify the Occupational Safety and Health Administration's (OSHA's) letter of June 14 to you on the applicability of the Process Safety Management (PSM) of Highly Hazardous Chemicals, 29 CFR 1910.119, standard to manufacturing processes involving workplace explosives. This clarification is made with respect to your production of missiles at McDonnell Douglas Corporation. Please disregard and discard the previous letter of interpretation.

As published in Volume 57, Number 26 of the Federal Register on Monday, February 24, 1992, 29 CFR 1910.109 - Explosives and Blasting Agents standard was amended to cover the manufacture of explosives under the PSM standard (See page 6403 of this Federal Register, a copy of which is enclosed for your use). In 1910.109(a)(3), an explosive is defined as

"any chemical compound, mixture, or device, the primary or common purpose of which is to function by explosion, i,e., with substantially instantaneous release of gas and heat, unless such compound, mixture, or device is otherwise specifically classified by the U.S. Department of Transportation (DOT); see 49 CFR Chapter I."

The term "explosives" includes all material which were formally classified as Class A, Class B and Class C explosives by DOT and are now classified by number designation. See the 49 CFR 173.53 table (enclosed) which compares old and new designations. Additionally, OSHA considers the manufacture of explosives to mean: mixing, blending, extruding, synthesizing, assembling, disassembling, and other activities involved in the making of a product or device which is intended to explode or contains DOT - classified explosive materials (as described above). In your letter you identified some missiles which are fabricated at McDonnell Douglas Corporation and which are explosive devices by the preceding definition.

The PSM standard covers the manufacturing of explosive materials as described above. Also, the PSM standard covers manufacturing processes when the resulting finished products or devices are intended to explode or they contain DOT - classified explosive materials (as described above). As a hypothetical example, an employer obtains an explosive device manufactured by another employer. This explosive device is a subassembly for a missile which is manufactured by the employer. Both employers must comply with the PSM standard.

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


Roger A. Clark, Director
Directorate of Compliance Programs