{"operation":"document","citation":"26-0015","title":"Mobile Power Solutions — Hazardous Materials Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"2026-05-22","effective_on":null,"summary":"26-0015 response to Mobile Power Solutions concerning 173.185.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-26-0015.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-26-0015.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-26-0015","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/2026-05/26-0015.pdf","body":"<<>>\n\n1200 New Jersey Avenue, SE\nWashington, DC 20590\nU.S. Department\nof Transportation\nPipeline and Hazardous\nMaterials Safety\nAdministration\nMay 22, 2026\nRory Pynenburg, PhD\nMobile Power Solutions\n9665 SW Allen Blvd\nSuite 110\nBeaverton, OR 97005\nReference No. 26-0015\nDear Dr. Pynenburg:\nThis letter is in response to your January 26, 2026 email requesting clarification of the\nHazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to testing\nrequirements for lithium-ion cells and batteries, in accordance with Section 38.3 of the United\nNations (UN) Manual of Tests and Criteria. Specifically, you request clarification of the UN\nManual of Tests and Criteria, Subsection 38.3.4.8, Test T.8: Forced discharge, as it relates to the\ndefinition of “disassembly” and “fire” during testing. You describe a scenario in which, during\nthe rest period following T.8 testing, a pouch cell’s envelope burst at a corner, exposing a small,\nsinged protrusion of internal components. You note that no visible flame was observed, and the\nmesh screen barrier placed 25 cm away was not penetrated. You ask whether this specific result\nconstitutes a test failure.\nIn accordance with Subsection 38.3.4.8.3, cells meet the T.8 testing requirement if there is no\ndisassembly and no fire during the test and within seven days after the test. Subsection 38.3.2.3\nstates “disassembly” means a rupture of the cell or battery case where solid components are\nejected. However, there is a note to the definition of “disassembly,\n” which states that during cell\nor component cell testing, ejection of internal components is acceptable provided the energy of\nthe ejected components does not penetrate a wire mesh screen (annealed aluminum wire with a\n0.25 mm diameter and grid density of 6 to 7 wires per cm) placed 25 cm from the cell. Based on\nyour observation that the mesh screen remained intact, and the components were merely exposed\nor protruding rather than forcefully ejected beyond the screen, it is the opinion of this Office that\nthe event described does not meet the criteria for “disassembly.” In addition, Subsection 38.3.2.3\nstates “fire” means that flames are emitted from the test cell or battery. You note that no visible\nflame was observed. While you state the internal material was singed, in the absence of a visible\nflame, it is the opinion of the Office this does not constitute a “fire” for the purposes of passing\nor failing the T.8 test.\n\n<<>>\n\nBased on your description that there was no disassembly (as defined by Subsection 38.3.2.3) and\nno visible flame, it is the opinion of this Office that the condition of the cell would likely not\nconstitute a failure of the T.8 test.\nI hope this information is helpful. Please contact us if we can be of further assistance.\nSincerely,\nAlexander Wolcott\nActing Chief, Regulatory Review and Reinvention Branch\nStandards and Rulemaking Division\n\n<<>>\n\nLarson, R.\n26-0115\nFrom: INFOCNTR (PHMSA)\nTo: Baker, Yul (PHMSA)\nCc: Hazmat Interps\nSubject: FW: Request for interpretation of section 38.3.4.8.\nDate: Tuesday, January 27, 2026 2:33:17 PM\nGood afternoon,\nPlease see the following request for a letter of interpretation. Let us know if you need anything\nelse.\nBest,\nAminah\nFrom: Rory Pynenburg \nSent: Monday, January 26, 2026 6:20 PM\nTo: INFOCNTR (PHMSA) \nCc: Jeremy Le Grand ; Spencer Poff\n; Chuck Weitzel \nSubject: Request for interpretation of section 38.3.4.8.\nYou don't often get email from rpynenburg@mobilepowersolutions.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.\nGood afternoon,\nI’m reaching out to request an interpretation of section 38.3.4.8.\nDuring the rest period following T.8 forced discharge testing a pouch cell had a corner of\nits envelope burst, exposing a small, singed protrusion of internal components. The\nburst did not break our mesh screen barrier. We did not witness visible flame during the\ntest, but the exposed internal material is singed. Picture attached for reference.\nT.8 requirements: Primary or rechargeable cells meet this requirement if there is no\ndisassembly and no fire during the test and within seven days after the test.\nDisassembly means a rupture of the cell or battery case where solid components are\n\n<<>>\n\nejected.\nNote: During cell or component testing, ejection of internal components is acceptable.\nEnergy of ejected components shall be limited and can be measured as follows:\n-will not penetrate a wire mesh screen (annealed aluminum wire with a diameter\nof .25mm and grid density of 6 to 7 wires per cm) placed 25 cm away from cell; or\n-it can be measured by a method demonstrated to be equivalent to the one\ndescribed in sub-paragraph (a) above.\nRupture means the mechanical failure of a cell container or battery case induced by an\ninternal or external cause, resulting in exposure or spillage but not ejection of solid\nmaterials.\nPlease advise if this constitutes a failure based on the standard.\nThank you,\nRory Pynenburg\nRory Pynenburg, PhD\nCTO\n9665 SW Allen Blvd, Suite 110,\nBeaverton, OR 97005\n503-645-6789\nwww.mobilepowersolutions.com\nrpynenburg@mobilepowersolutions.com\nThe information contained in this message may be privileged and confidential. It is\nintended to be read only by the individual or entity to whom it is addressed or by their\ndesignee. If the reader of this message is not the intended recipient, you are on notice\nthat any distribution of this message, in any form, is strictly prohibited. If you have\nreceived this message in error, please immediately notify the sender and delete or\ndestroy any copy of this message. This message was encrypted with TLS.\n\n<<>>\n\nAK-\n- 1982\nAK-1982\n01-28\n0:-29\nW...\n\n<<>>\n\n\n\n<<>>\n\n\n\n<<>>\n\nAK-1 782\n01-29","truncated":false,"body_characters":6082}