{"operation":"document","citation":"25-0141","title":"Thatcher Company of California — Hazardous Materials Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"2026-03-09","effective_on":null,"summary":"25-0141 response to Thatcher Company of California concerning 173.202, 173.24, 180.205, 180.209.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-25-0141.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-25-0141.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-25-0141","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/2026-03/250141.pdf","body":"<<>>\n\n1200 New Jersey Avenue, SE\nWashington, DC 20590\nU.S. Department\nof Transportation\nPipeline and Hazardous\nMaterials Safety\nAdministration\nMarch 9, 2026\nAmes Ettinger\nLaboratory Manager\nThatcher Company of California\n8625 Unsworth Ave\nSacramento, CA 95828\nReference No. 25-0141\nDear Mr. Ettinger:\nThis letter is in response to your November 14, 2025 email requesting clarification of the\nHazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the use of\nDepartment of Transportation (DOT)-4L welded insulated cylinders for the transportation of a\n5% solution of “UN1833, Sulfurous acid, 8, PG II” in accordance with packaging authorized in\n§ 173.202. You explain that § 173.202(c) authorizes the following single packagings: “Cylinders,\nspecification, as prescribed for any compressed gas, except for Specifications 8 and 3HT.” In\naddition, you state while the requirements in § 173.202(c) do not explicitly prohibit the use of\nDOT-4L specification cylinders you ask whether these cylinders may still be used because they\nare designed for the transportation of liquefied gases and “UN1833” is a liquid hazardous\nmaterial.\nWe have paraphrased and answered your questions as follows:\nQ1. Is a DOT-4L cylinder an authorized cylinder specification under § 173.202(c) for the\ntransportation of “UN1833”? If not, would this require submitting a special permit\nrequest to perform this function?\nA1. Yes. Section 173.202 authorizes non-bulk packagings for transportation of liquid\nhazardous materials in Packing Group II. Thus, in accordance with § 173.202(c) which\nauthorizes specification cylinders, and except for transportation by passenger aircraft, a\nDOT-4L cylinder adhering to applicable requirements of the HMR (e.g., § 173.24(b))\nmay be used for the transportation of a “UN1833” material.\nQ2. If a DOT-4L cylinder is considered an authorized packaging under § 173.202, are the\ncylinders excepted from requalification requirements in accordance with § 180.209, even\nthough they are used for a liquid?\n\n<<>>\n\nA2. Yes. When a DOT-4L cylinder is used for liquid transport under § 173.202, it is\nconsidered an authorized packaging. Because DOT-4L cylinders are excluded from the\nrequalification table listed in § 180.209(a), they are not subject to periodic requalification\ntesting. However, this does not except the offeror or carrier from other HMR safety\nstandards, such as the general inspection and maintenance requirements found in\n§ 180.205(e).\nI hope this information is helpful. Please contact us if we can be of further assistance.\nSincerely,\nDirk Der Kinderen\nChief, Standards Development Branch\nStandards and Rulemaking Division\n\n<<>>\n\nBaker, Y.\n25-0141\nFrom: INFOCNTR (PHMSA)\nTo: Baker, Yul (PHMSA)\nCc: Hazmat Interps\nSubject: 173.202\nDate: Friday, November 14, 2025 13:58:02\nLetter of Interpretation Request - FW: Request for Formal Interpretation - Use of DOT-4L Cylinders under 49 CFR\nGood afternoon,\nPlease see the following interpretation request. Let us know if you need anything else.\nBest,\nJanaye\nFrom: Ames Ettinger \nSent: Friday, November 14, 2025 11:00 AM\nTo: INFOCNTR (PHMSA) \nCc: John Riley \nSubject: Request for Formal Interpretation - Use of DOT-4L Cylinders under 49 CFR 173.202\nYou don't often get email from ames.ettinger@tchem.com. Learn why this is important\nCAUTION: This email originated from outside of the Department of Transportation (DOT). Do\nnot click on links or open attachments unless you recognize the sender and know the content\nis safe.\nDear PHMSA Standards and Rulemaking Division,\nI am requesting a formal letter of interpretation regarding the use of DOT-4L cylinders for\ntransportation of sulfurous acid, 5% solution (UN 1833) under 49 CFR 173.202 - Non-bulk\npackaging requirements for liquid hazardous materials in Packing Group II.\nSpecifically, 49 CFR 173.202(c) authorizes “cylinders, specification, as prescribed for any\ncompressed gas, except for Specifications 8 and 3HT,” without explicitly prohibiting the DOT-\n4L specification. DOT-4L cylinders, however, are designed for cryogenic refrigerated liquefied\ngases under 49 CFR 178.57.\nWe request PHMSA’s interpretation on the following point:\n1. Is a DOT-4L cylinder considered an authorized cylinder specification under 49 CFR 173.202\nfor the transportation of sulfurous acid (UN 1833), or would this constitute a non-standard use\nrequiring a PHMSA special permit?\n2. If DOT-4L cylinders are considered authorized under 173.202, would they continue to be\nexempt from requalification under 49 CFR 180.209, as currently specified for DOT-4L\ncylinders?\n\n<<>>\n\nThank you for your clarification.\nPlease advise if any additional information is needed.\nAmes Ettinger\nLaboratory Manager\nThatcher Company of California\nDirect: 435-668-5369\nMailing:\n8625 Unsworth Ave, Sacramento CA 95828\nThe information contained in this e-mail message, and any attachments to it, contain\nconfidential, proprietary, privileged, or otherwise secret information. If you are not the\nintended recipient, or believe that you may have received this email or attachments in\nerror, any dissemination, use, review, distribution, printing or copying of the information\ncontained in this e-mail message and any attachments to it are strictly prohibited. If you\nhave received this communication in error, please notify us by reply e-mail or telephone\nand immediately and permanently delete the message and any attachments. Please\ninclude in your notice that the message and any attachments have been deleted. Thank\nyou.","truncated":false,"body_characters":5616}