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.



March 14, 2000

J. Lewis Slaughter, P.E.
Senior Chemical Engineer
Trigon Engineering Consultants, Inc.
313 Gallimore Dairy Rd.
Greensboro, NC 27409

Dear Mr. Slaughter:

Thank you for your January 6, 2000 facsimile letter to the Occupational Safety and Health Administration's (OSHA's) Directorate of Compliance Programs (DCP). You have a question regarding OSHA's Process Safety Management of Highly Hazardous Chemicals; Explosives and Blasting Agents Standard (PSM), 29 CFR 1910.119. You have a specific question regarding the application of the standard to a liquefied petroleum gas (LPG) bottle filling process.

Question: Does the PSM standard apply to the LPG bottle filling process which is listed below?

Product and Process



  1. The process will be an assembly line process to fill consumer size LPG bottles for wide area distribution;
  2. The facility will be in accordance with National Fire Protection Association's Standard for the Storage and Handling of Liquefied Petroleum Gases, NFPA 58 and OSHA 29 CFR 1910.110, Storage and Handling of Liquefied Petroleum Gases;
  3. The product is LPG-filled returnable bottles typically used in gas fueled barbecue grills. The bottles each have a volume of about five (5) gallons and the quantity of LPG will be limited to less than 20 pounds;
  4. LPG bulk inventory stored on-site will exceed 10,000 pounds in an isolated tank farm;
  5. A production building will be dedicated to inspection and reconditioning of returned bottles and automatic filling of new and reconditioned bottles followed by quality assurance inspection;
  6. Finished product bottles will be stored in a separate open sided building remote from both LPG bulk storage and the production building;
  7. LPG will be pumped underground to the production building; and
  8. Bottle reconditioning and filling activities will be isolated from each other by the requisite separations in accordance with the codes cited above.



Response: The LPG bottle filling process you described above is covered by PSM. The reasons for PSM coverage of the listed process include the following:



  1. LPG is a PSM covered material - flammable gas;
  2. Greater than a threshold quantity of flammable gas (10,000 pounds) exists in the process. The covered process includes at least the LPG bulk storage tank(s) and the interconnected bottle filling operation.

    NOTE: Equipment that is interconnected utilizing underground piping does not negate the interconnected relationship. The finished product storage area could be a covered process by itself if it contains an aggregate quantity of LPG greater than 10,000 pounds. Furthermore, if the operation contains interconnected and/or separate vessels (e.g., bottle reconditioning or finished product storage area) which are located such that a flammable gas (e.g., LPG) could be involved in a potential release, then such interconnected and/or separate vessels would be considered part of the covered process;
  3. Requisite activities are conducted which define a covered process including storage, on-site movement and handling; and
  4. None of the PSM exemptions apply, including the retail facilities exemption [29 CFR 1910.119(a)(2)(i)]. The products (LPG 20 pound bottles/cylinders) from this process are not sold to end users (as per your January 19, 2000 teleconference with a member of my staff). Rather the products are sold via a "wide area distribution" primarily to large retail distributors/stores such as home improvement centers, hardware stores, convenience stores, etc. These retail distributors/stores in turn sell the LPG bottles to consumers/end users. Therefore, the PSM retail exemption does not apply.

Please note that Section 18 of the OSH Act encourages States to assume responsibility for their own occupational safety and health programs under a plan approved and closely monitored by Federal OSHA. The North Carolina Department of Labor is operating such a plan and is responsible for the enforcement of its own occupational safety and health standards and the investigation of workplace complaints throughout the State. All of North Carolina's job safety and health standards, including interpretations, are identical to or at least as effective as the comparable Federal OSHA.

In addition, North Carolina offers free on-site consultation services to those employers who request guidance on compliance with occupational safety and health standards. For information regarding either the consultation services or information concerning the North Carolina program, please contact the State directly at the following address:

[Bureau of Consultative Services
NC Department of Labor—OSHA Division
4 West Edenton Street
Raleigh, North Carolina 27601-1092
Phone: (919) 807-2905
FAX: (919) 807-2902
Website: http://www.nclabor.com ]

Thank you for your interest in occupational safety and health. We hope you find this information helpful. Please be aware that OSHA's enforcement guidance is subject to periodic review and clarification, amplification, or correction. Such guidance could also be affected by subsequent rulemaking. In the future, should you wish to verify that the guidance provided herein remains current, you may consult OSHA's website at http://www.osha.gov. If you have any further questions, please feel free to contact the [Office of General Industry Enforcement at (202) 693-1850].


Richard E. Fairfax, Director
[Directorate of Enforcement Programs]

[Corrected 6/2/2005]