Southwest Airlines Co. — Hazardous Materials Safety Interpretation

Page 11200 New Jersey Avenue, SE Washington, DC 20590 U.S. Department of Transportation Pipeline and Hazardous Materials Safety Administration February 23, 2026 Todd Hargrove Hazardous Materials Program Manager Southwest Airlines Co. P.O. Box 36611 Dallas, Texas 75235 Reference No. 25-0120 Dear Mr. Hargrove: This letter is in response to your August 29, 2025 email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to battery-powered heat- producing devices. Specifically, you ask about the on-board use (i.e., use aboard a passenger aircraft) of a lithium ion battery-powered food warmer in the context of battery-powered heat- producing devices subject to § 175.10(a)(14). We have paraphrased and answered your questions as follows: Q1. Is a lithium ion battery-powered food warmer considered to be a portable electronic device rather than a heat-producing device? A1. Yes. It is the opinion of this Office that if the lithium-ion battery-powered device does not generate an amount of heat sufficient to be a source of ignition, it is not a “heat producing device” subject to § 175.10(a)(14). However, it should be considered a battery- powered device that would be subject to the requirements of § 175.10(a)(18) as a “portable electronic device.” Q2. Does § 175.10(a)(14) prohibit a passenger or crewmember from using a lithium-ion battery-powered food warmer that is intentionally activated to warm food during flight? A2. Yes. However, for electronic devices subject to § 175.10(a)(18), use during flight is allowed when the device is for personal use. Whereas § 175.10(a)(14) requires the heating element, battery, or other component to be isolated to prevent unintentional activation. Furthermore, battery powered heat-devices subject to § 175.10(a)(14) may not be intentionally activated in flight.#

Page 2Note also that in addition to the HMR requirements, passengers and air carriers must comply with all applicable Federal Aviation Administration (FAA) requirements. This includes using safety management system (SMS) processes and coordination with respective certificate management offices (CMO), as well as complying with 14 CFR § 91.21 requirements that address operation of portable electronic devices aboard the aircraft and the possible effects to aircraft systems. Information and guidance to assist with compliance of this requirement can be found in Advisory Circular (AC) 91.21-1D, titled “Use of Portable Electronic Devices Aboard Aircraft.” For additional information regarding the FAA requirements contact the FAA’s Office of Hazardous Materials Safety at hazmatinfo@faa.gov. I hope this information is helpful. Please contact us if we can be of further assistance. Sincerely, Dirk DerKinderen Chief, Standards Development Branch Standards and Rulemaking Division#

Page 3Southwest Airlines Co. Todd Hargrove Safety & Security PO Box 36611 Dallas, Texas 75235 Phone:469-603-4813 Casey, C. 25-0120 August 29, 2025 Pipeline and Hazardous Materials Safety Administration Standards and Rulemaking Division ATTN: PHH-10 U.S. Department of Transportation East Building 1200 New Jersey Avenue, SE Washington, DC 20590-0001 Re: Interpretation Letter Request I am writing to obtain clarification regarding the acceptance of a battery powered heat-producing device and onboard use based on 49 CFR Part 175.10(a)(14) A prior interpretation letter (10-0267) mentioned a heat-producing device would be one that produced an amount of heat sufficient to be a source of ignition. 175.10 also mentions unintentional activation. The below questions are regarding a food warmer that would not produce enough heat to be a source of ignition and would be intentionally activated. Would a lithium-ion battery operated food warmer be considered a portable electronic device? Would 175.10(a)(14) prohibit a passenger or crewmember from using a lithium-ion battery operated food warmer that is intentionally activated to warm their food during flight? Thank you for your assistance in this matter. Feel free to contact me at Todd.Hargrove@wnco.com or 469-603-4813 if further clarification is needed. Sincerely, Todd Hargrove Hazardous Materials Program Manager#

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