{"operation":"document","citation":"24-0104","title":"AECOM Technical Services, Inc. — Hazardous Materials Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"2025-03-27","effective_on":null,"summary":"24-0104 response to AECOM Technical Services, Inc. concerning 173.22.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-24-0104.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-24-0104.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-24-0104","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/2025-03/240104_0.pdf","body":"<<>>\n\nU.S. Department\nof Transportation\nPipeline and Hazardous\nMaterials Safety\nAdministration\n1200 New Jersey Avenue, SE\nWashington, DC 20590\nMarch 27, 2025\nMs. Carolyn Norris\nProject Manager\nAECOM Technical Services, Inc.\n5438 Wade Park Boulevard\nSuite 200\nRaleigh, NC 27607\nReference No. 24-0104\nDear Ms. Norris:\nThis letter is in response to your October 24, 2024, letter requesting clarification of the\nHazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to classification of\nDivision 4.2 self-heating substances. Specifically, is the alternative to the testing method\ndescribed in the United Nations (UN) Manual of Tests and Criteria described in your letter have\ntechnical merit in this Office’s opinion? According to your letter, the material to be tested\nexhibits the characteristic of a self-heating material; though, the exact test as described in the UN\nManual of Tests & Criteria cannot be performed.\nYes. The method described in the UN Manual of Tests and Criteria, Test N.4—test method for\nself-heating substances—requires testing of samples in 25 mm and 100 mm cubes at discrete\ntemperatures to establish whether a material meets the definition of a Division 4.2 self-heating\nmaterial and to determine the packing group. You state that your alternative method mimics the\ntest set out in the UN Manual of Tests and Criteria for the Division 4.2 self-heating material\nexcept that—due to the form of the material—you did not use a 25 mm or 100 mm sample cube.\nYou state that the test was performed as a thin layer on a substrate measuring 152.5 mm x\n152.5 mm—the form it will be in when offered for transportation. You note that your testing\ndemonstrated that in this form, the material exhibits self-heating behavior.\nIn accordance with § 173.22 of the HMR, it is the shipper’s responsibility to classify a hazardous\nmaterial. This Office generally does not perform this function. However, based on the test data\nas described in your letter, we agree with your determination that it is appropriate to class the\nmaterial—when offered as a thin layer on a substrate measuring 152.5 mm x 152.5 mm—as a\nDivision 4.2 self-heating material.\n\n<<>>\n\nI hope this information is helpful. Please contact us if we can be of further assistance.\nSincerely,\nT. Glenn Foster\nChief, Regulatory Review and Reinvention Branch\nStandards and Rulemaking Division\n\n<<>>\n\nPollack\n24-0104\nFrom: INFOCNTR (PHMSA)\nTo: Dodd, Alice (PHMSA)\nCc: Hazmat Interps\nSubject: FW: Request for DOT PHMSA Regulatory Interpretation Division 4.2 Self Heating Substance UN Test\nDate: Friday, October 25, 2024 12:13:56 PM\nAttachments: Request for DOT PHMSA Interpretation Self Heating Substance UN Test 10242024.pdf\nHello Hazmat Interps,\nPlease see the attached request for a letter of interpretation.\nThanks,\nJanaye\nFrom: Norris, Carolyn \nSent: Thursday, October 24, 2024 11:26 AM\nTo: INFOCNTR (PHMSA) \nSubject: Request for DOT PHMSA Regulatory Interpretation Division 4.2 Self Heating Substance UN\nTest\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.\nMr. Shane Kelley and Hazardous Materials Information Center:\nSee attached request for a formal DOT PHMSA Interpretation letter concerning the Division 4.2\nSelf Heating Substance UN Test.\nLet me know if you have any questions.\nThanks,\nCarolyn E. Norris, DGSA\nSenior Project Scientist/Project Manager, EHS Department\nD +1-919-461-1238\ncarolyn.norris@aecom.com\nAECOM\n5438 Wade Park Boulevard\nSuite 200\nRaleigh, NC 27607, USA\nT +1-919-461-1100\naecom.com\nBuilt to deliver a better world\nLinkedIn Twitter Facebook Instagram\n\n<<>>\n\nAECOM Technical Services, Inc.\n5438 Wade Park Boulevard\nSuite 200\nRaleigh, NC 27607\n(919) 461-1100\nwww.aecom.com\nOctober 24, 2024\nMr. Shane Kelley\nDirector, Office of Hazardous Materials Standards and Rulemaking Division\nU.S. Department of Transporta on/Pipeline and Hazardous Materials Safety Administra on (PHH-10)\nEast Building, 2nd Floor\n1200 New Jersey Avenue, SE\nWashington, DC 20590-0001\nPhone: (202) 366-8553\nE-mail: infocntr@DOT.gov\nSubject: Request for concurrence that due to the limita on of form, tes ng conducted on a solid\nmaterial (substrate with Material A applied in a thin layer) rather than in a 25 millimeter (mm)\nor 100 mm sample cube may be used to establish whether a solid material should be classified\nas a Division 4.2 self-hea ng substance.\nDear Mr. Kelley:\nIn 49 CFR 173.124(b)(2), a Division 4.2 self-hea ng material is defined as:\nA self-hea ng material is a material that through a process where the gradual reac on of that\nsubstance with oxygen (in air) generates heat. If the rate of heat produc on exceeds the rate of\nheat loss, then the temperature of the substance will rise which, a er an induc on me, may\nlead to self-igni on and combus on. A material of this type which exhibits spontaneous igni on\nor if the temperature of the sample exceeds 200oC (392oF) during the 24-hour test period when\ntested in accordance with the UN Manual of Tests and Criteria…is classed as a Division 4.2\nmaterial.\nWe have a high surface-area substrate with Material A applied in a thin layer that as shipped behaves like\na Division 4.2 Self-hea ng material PGII. However, we cannot perform the test set out in the most\ncurrent UN Manual of Test & Criteria for the Division 4.2 Self-hea ng Substances (33.4.3.3) because we\ncannot form the material into the cube of the material (25 mm or 100 mm sample cube) as required by\nthe test due to its form (thin layer applied on a substrate). The only varia on from the UN test is not\nforming it into this cube.\nNote that Material A itself has been tested by the manufacturer and does not meet the UN test criteria\nas a Division 4.2 self-hea ng material. The inert substrate alone does not meet the UN test criteria as a\nDivision 4.2 self-hea ng material. Only when Material A is applied in a thin layer on the substrate does it\nexhibit these self-hea ng proper es at a temperature exceeding 60oC. Note also that we eliminated any\npyrophoric characteris c through tes ng. This substrate with Material A applied only exhibits\nDivision 4.2 self-hea ng proper es.\nThe test we ran mimics the test set out in the UN Manual of Test & Criteria for the Division 4.2\nself-hea ng material except we did not use a 25 mm or 100 mm sample cube due to the form of the\nmaterial. We ran the test on Material A applied as a thin layer on the substrate (15.25 cen meter (cm) x\n1/1\n\n<<>>\n\nMr. Shane Kelley\nDirector, Office of Hazardous Materials Standards and Rulemaking\nOctober 24, 2024\n15.25 cm cube), as it would be shipped, and found it exhibits self-hea ng behavior. (See graphs of test\nresults below.) May the test we conducted be used to support the Division 4.2 self-hea ng classifica on\nof this material, even though the exact test as described in the UN Manual of Tests & Criteria was not\nfollowed?\nNote that there is a le er of interpreta on (08-0214) that allows an alterna ve test for classifying as a\nself-hea ng material, although it was used to support classifica on as not self-hea ng, rather than\nself-hea ng.\nSubstrate With Material A Applied Self-Heating Test\n250\nHeat Applied\n200\nTemperature (°C)\n150\n100\nSubstrate with Material A\nApplied\n50\n0\n0:00:00 2:00:00 4:00:00 6:00:00 8:00:00 10:00:00 12:00:00\nTime (h:mm:ss)\nWe appreciate your considera on and response to this regulatory interpreta on request.\nSincerely,\nAECOM Technical Services, Inc.\nCarolyn Norris\nProject Manager\n1/2","truncated":false,"body_characters":7642}