# Fleet Services Business Department — Hazardous Materials Safety Interpretation **Citation:** 15-0157 **Type / status:** guidance / guidance **Agency:** Pipeline and Hazardous Materials Safety Administration **Effective:** Not stated **Published:** 2015-10-29 15-0157 response to Fleet Services Business Department concerning 173.29. ## Document text <<>> U.S. Department 1200 New Jersey Avenue SE of Transportation Washington. DC 20590 Pipeline and Hazardous Materials Safety Administration OCT 29 2015 Ms. Elizabeth Carson Department of Transportation Program Lead Fleet Services Business Department P.O. Box 5800 MS0950 Albuquerque, New Mexico 87185-0950 Reference No. 15-0157 Dear Ms. Carson: This is in response to your July 14, 2015 letter requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the shipment of an emptied non-specification pressure cylinder used to store hydrogen gas at your facility. In your letter, you state that you have a hydrogen storage system that incorporates mounted non- Department of Transportation (DOT) specification cylinders. The system is filled with 12,690 pounds per square inch (psi) of Hydrogen while at a fixed location. Your intent is to vent and purge the cylinders with nitrogen gas before transporting the cylinders by highway. You add that this process will leave a 97% Nitrogen / 3% Hydrogen gas composition at less than 29 psi inside the cylinders. You ask if the non-DOT specification cylinders that are cleaned and purged as you describe would constitute an empty package under § 173.29(b)(2) (iv)(B). Provided that the empty packaging described in your letter is cleaned and purged in accordance with § 173.29(b)(2)(iv)(B), the answer is yes. In addition, § 173.29(b)(2)(ill) states that an empty packaging that is refilled with a material which is non-hazardous to such an extent that any residue remaining in the packaging no longer poses a hazard is not subject to the requirements of the HMR. Please note that for purposes of the HMR, cleaned and purged means no residual hazardous material or vapor remain in a container. The procedure presented in your letter appears to leave the cylinders sufficiently cleaned of residue and any of the hazard class definitions in the HMR. I hope this satisfies your request. Sincerely, Tens sot T. Glenn Foster Chief, Regulatory Review and Reinvention Branch Standards and Rulemaking Division <<>> DOT/RSPA /OHMS Sandia National Laboratories Operated for the U.S. Department of Energy by Title: DOT Program Administrator Name: Elizabeth Carson 15 JUL 15 PM 3: 30 Sandia Corporation P.O. Box 5800 Albuquerque, NM 87185- Fax: (505) 284-5490 Phone: (505)845-9845 Email:eccarso@sandia.gov Andrewes July 14, 2015 §173.29(b)(2)(v) (B) Associate Administrator for Hazardous Materials Safety Attention: Special Permits PHH-30 Packaging General Pipeline and Hazardous Materials Safety Administration 15-0157 U.S. Department of Transportation 1200 New Jersey Avenue, SE Washington, DC 20590-0001 To whom it may concern: My name is Elizabeth Carson. I work for a private motor carrier, Sandia National Laboratories' as the DOT Program Administrator, under USDOT 545058 with hazmat certification (HM Company ID 066448) through 6/30/2017, as a shipper and transporter. We have locations in New Mexico, California and Nevada. Our California site has entered into a project with the California Air Resource Board with regards to hydrogen testing for vehicles. We are in the process of commissioning the fabrication of a system which consists of a tandem axle enclosed cargo trailer (GVWR 7,000 pounds). The unit will contain a gaseous hydrogen storage system that incorporates permanently mounted non-DOT specification cylinders. While in use, but at a fixed location, the storage system may be filled with up to 12,690 psig of hydrogen gas. Our intent is to vent and purge the cylinders using nitrogen gas before transporting the trailer on U.S. roadways. The pressure in the cylinders will be reduced to less than 29 psig at 20° C in a series of steps. The gas composition after the final step will be 97% nitrogen / 3% hydrogen, which by our determination meets the criteria for classification as a Division 2.2 non-flammable gas. Any markings and labels on the cylinders will not be visible during transport. The cylinders are permanently mounted and will not be unloaded at any location where the trailer is used. Hazardous shipping papers will not be used when the trailer is transported. This letter is to request interpretation of 49CFR part 173.29(b) (2) (iv)(B). Namely, can non-DOT specification cylinders containing the Division 2.2 non-flammable gas described above be transported as empty packaging? Would the above procedure satisfy the regulations stated in 49 CFR part 173.29(b)(2) to sufficiently clean the hydrogen cylinders of all residue and purge them of vapors to remove any potential hazard, thereby making the cylinders acceptable for "empty packaging" in commerce? In order to maintain full compliance. with all federal hazardous material regulations, we are requesting a written interpretation specific to the aforementioned product and purpose. I look forward to your reply. Exceptional Service in the National Interest <<>> - 2- I greatly appreciate your time and consideration. • ( Sandia National Laboratories Oporated or the United States Departmen: of Energy by Supow Chan Management Logistios Sincerely, lichth Carton Elizabeth Carson, DOT Program Lead Fleet Services Business Department P.O. Box 5800, MS0950 Albuquerque, New Mexico 87185-0950 Copy to: Terry Johnson Jack Euske Mike Starr ## Provenance - Official: Yes - Source: - Source ID: `phmsa` - SHA-256: `b32f99875d1c6c5ee4758259c52d8ee93bc2e9eca013201f87ef17a69eb643ff` - Retrieved: 2026-08-20T00:59:31.977Z - Exported: 2026-08-23T01:01:58.062Z - Document slug: `phmsa-interpretation-15-0157` ### Source metadata ```json { "materialSubtype": "interpretation", "interpretationArea": "hazardous_materials", "representation": "full_text_from_official_pdf", "companies": [ "Fleet Services Business Department" ], "individuals": [ "Ms. Elizabeth Carson" ], "refIds": [ "15-0157" ], "catalogDates": [ "2015-10-29" ], "catalogParts": [ 173 ], "catalogRowCount": 1, "sourceRecordUrls": [ "https://www.phmsa.dot.gov/node/60666" ], "linkedAttachmentUrls": [], "unavailableResponseUrls": [], "duplicateRepresentationUrls": [], "citedSections": [ "173.29", "173.29(b)(2)" ], "catalogPageUrls": [ "https://www.phmsa.dot.gov/regulations/title49/section/17329" ], "pdfUrls": [ "https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretation%20Files/2015/150157.pdf" ], "representations": [ { "viewUrl": "https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretation%20Files/2015/150157.pdf", "detailUrl": null, "detailHtmlPath": null, "pdfUrl": "https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretation%20Files/2015/150157.pdf", "pdfArtifactPath": "data/sources/phmsa-interpretations/15-0157-ebfded43cb.pdf", "pdfArtifactSha256": "a2cf80f551a596ab1c3cb3353590b92fa449cfb7b13bc5a69a555d45154ceb6e", "extractedTextPath": "data/sources/phmsa-interpretations/15-0157-ebfded43cb.v2.txt", "extractedTextSha256": "4904513f7921760cf76b36587996e168764a8b5fb620a8f73293232abde2775f", "pageCount": 3, "extractionVersion": 2 } ], "caveat": "Interpretations apply regulations to the facts presented and do not create independently enforceable requirements.", "jurisdiction": "US" } ```