# AECOM Technical Services, Inc. — Hazardous Materials Safety Interpretation - **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:** Not available - **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:** <<>> U.S. Department of Transportation Pipeline and Hazardous Materials Safety Administration 1200 New Jersey Avenue, SE Washington, DC 20590 March 27, 2025 Ms. Carolyn Norris Project Manager AECOM Technical Services, Inc. 5438 Wade Park Boulevard Suite 200 Raleigh, NC 27607 Reference No. 24-0104 Dear Ms. Norris: This letter is in response to your October 24, 2024, letter requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to classification of Division 4.2 self-heating substances. Specifically, is the alternative to the testing method described in the United Nations (UN) Manual of Tests and Criteria described in your letter have technical merit in this Office’s opinion? According to your letter, the material to be tested exhibits the characteristic of a self-heating material; though, the exact test as described in the UN Manual of Tests & Criteria cannot be performed. Yes. The method described in the UN Manual of Tests and Criteria, Test N.4—test method for self-heating substances—requires testing of samples in 25 mm and 100 mm cubes at discrete temperatures to establish whether a material meets the definition of a Division 4.2 self-heating material and to determine the packing group. You state that your alternative method mimics the test set out in the UN Manual of Tests and Criteria for the Division 4.2 self-heating material except that—due to the form of the material—you did not use a 25 mm or 100 mm sample cube. You state that the test was performed as a thin layer on a substrate measuring 152.5 mm x 152.5 mm—the form it will be in when offered for transportation. You note that your testing demonstrated that in this form, the material exhibits self-heating behavior. In accordance with § 173.22 of the HMR, it is the shipper’s responsibility to classify a hazardous material. This Office generally does not perform this function. However, based on the test data as described in your letter, we agree with your determination that it is appropriate to class the material—when offered as a thin layer on a substrate measuring 152.5 mm x 152.5 mm—as a Division 4.2 self-heating material. <<>> I hope this information is helpful. Please contact us if we can be of further assistance. Sincerely, T. Glenn Foster Chief, Regulatory Review and Reinvention Branch Standards and Rulemaking Division <<>> Pollack 24-0104 From: INFOCNTR (PHMSA) To: Dodd, Alice (PHMSA) Cc: Hazmat Interps Subject: FW: Request for DOT PHMSA Regulatory Interpretation Division 4.2 Self Heating Substance UN Test Date: Friday, October 25, 2024 12:13:56 PM Attachments: Request for DOT PHMSA Interpretation Self Heating Substance UN Test 10242024.pdf Hello Hazmat Interps, Please see the attached request for a letter of interpretation. Thanks, Janaye From: Norris, Carolyn Sent: Thursday, October 24, 2024 11:26 AM To: INFOCNTR (PHMSA) Subject: Request for DOT PHMSA Regulatory Interpretation Division 4.2 Self Heating Substance UN Test CAUTION: This email originated from outside of the Department of Transportation (DOT). Do not click on links or open attachments unless you recognize the sender and know the content is safe. Mr. Shane Kelley and Hazardous Materials Information Center: See attached request for a formal DOT PHMSA Interpretation letter concerning the Division 4.2 Self Heating Substance UN Test. Let me know if you have any questions. Thanks, Carolyn E. Norris, DGSA Senior Project Scientist/Project Manager, EHS Department D +1-919-461-1238 carolyn.norris@aecom.com AECOM 5438 Wade Park Boulevard Suite 200 Raleigh, NC 27607, USA T +1-919-461-1100 aecom.com Built to deliver a better world LinkedIn Twitter Facebook Instagram <<>> AECOM Technical Services, Inc. 5438 Wade Park Boulevard Suite 200 Raleigh, NC 27607 (919) 461-1100 www.aecom.com October 24, 2024 Mr. Shane Kelley Director, Office of Hazardous Materials Standards and Rulemaking Division U.S. Department of Transporta on/Pipeline and Hazardous Materials Safety Administra on (PHH-10) East Building, 2nd Floor 1200 New Jersey Avenue, SE Washington, DC 20590-0001 Phone: (202) 366-8553 E-mail: infocntr@DOT.gov Subject: Request for concurrence that due to the limita on of form, tes ng conducted on a solid material (substrate with Material A applied in a thin layer) rather than in a 25 millimeter (mm) or 100 mm sample cube may be used to establish whether a solid material should be classified as a Division 4.2 self-hea ng substance. Dear Mr. Kelley: In 49 CFR 173.124(b)(2), a Division 4.2 self-hea ng material is defined as: A self-hea ng material is a material that through a process where the gradual reac on of that substance with oxygen (in air) generates heat. If the rate of heat produc on exceeds the rate of heat loss, then the temperature of the substance will rise which, a er an induc on me, may lead to self-igni on and combus on. A material of this type which exhibits spontaneous igni on or if the temperature of the sample exceeds 200oC (392oF) during the 24-hour test period when tested in accordance with the UN Manual of Tests and Criteria…is classed as a Division 4.2 material. We have a high surface-area substrate with Material A applied in a thin layer that as shipped behaves like a Division 4.2 Self-hea ng material PGII. However, we cannot perform the test set out in the most current UN Manual of Test & Criteria for the Division 4.2 Self-hea ng Substances (33.4.3.3) because we cannot form the material into the cube of the material (25 mm or 100 mm sample cube) as required by the test due to its form (thin layer applied on a substrate). The only varia on from the UN test is not forming it into this cube. Note that Material A itself has been tested by the manufacturer and does not meet the UN test criteria as a Division 4.2 self-hea ng material. The inert substrate alone does not meet the UN test criteria as a Division 4.2 self-hea ng material. Only when Material A is applied in a thin layer on the substrate does it exhibit these self-hea ng proper es at a temperature exceeding 60oC. Note also that we eliminated any pyrophoric characteris c through tes ng. This substrate with Material A applied only exhibits Division 4.2 self-hea ng proper es. The test we ran mimics the test set out in the UN Manual of Test & Criteria for the Division 4.2 self-hea ng material except we did not use a 25 mm or 100 mm sample cube due to the form of the material. We ran the test on Material A applied as a thin layer on the substrate (15.25 cen meter (cm) x 1/1 <<>> Mr. Shane Kelley Director, Office of Hazardous Materials Standards and Rulemaking October 24, 2024 15.25 cm cube), as it would be shipped, and found it exhibits self-hea ng behavior. (See graphs of test results below.) May the test we conducted be used to support the Division 4.2 self-hea ng classifica on of this material, even though the exact test as described in the UN Manual of Tests & Criteria was not followed? Note that there is a le er of interpreta on (08-0214) that allows an alterna ve test for classifying as a self-hea ng material, although it was used to support classifica on as not self-hea ng, rather than self-hea ng. Substrate With Material A Applied Self-Heating Test 250 Heat Applied 200 Temperature (°C) 150 100 Substrate with Material A Applied 50 0 0:00:00 2:00:00 4:00:00 6:00:00 8:00:00 10:00:00 12:00:00 Time (h:mm:ss) We appreciate your considera on and response to this regulatory interpreta on request. Sincerely, AECOM Technical Services, Inc. Carolyn Norris Project Manager 1/2 - **truncated:** false - **body characters:** 7642