Thermal Runaway Incidents – Safety Procedures for Burns and Potential Smoke Inhalation
(Cardno ChemRisk, Arlington, VA)
Thermal runaway is a failure mode in lithium-ion batteries that occurs when exothermic reactions are induced by short-circuiting, excessive heat, or physical distress to the batteries. The process can generate extreme heat that can melt the battery and surrounding hardware and even cause the device to catch fire. Thermal runaway in electronic devices is a concern for regulatory agencies, cargo transportation providers, commercial airlines, device and battery manufacturers, consumers carrying these devices, and others. In the occupational setting, physical hazards such as burns can be lessened via training employees, providing fire extinguishing media such as sand, using personal protective equipment, and battery charge control. Aside from physical hazards in the immediate area of a thermal runaway event, a potential human health risk exists from chemicals generated by the reaction, one of which can be hydrogen fluoride. This risk has not been quantitatively evaluated in the available scientific literature. We performed a screening-level analysis aimed to assess exposure and characterize the health risk associated with hydrogen fluoride released during a thermal runaway event on an airplane. Briefly, the fluorine mass content in a lithium-ion cell phone battery was derived from manufacturers’ specification sheets. A well-mixed box model was then used to conservatively estimate the airborne concentration of hydrogen fluoride generated in a commercial airplane cabin and cockpit. Using very conservative assumptions, potential 10-minute peak exposures to hydrogen fluoride from a thermal runaway event ranged from 1.1 to 7.1 mg/m3 in the cabin and 0.5 to 3.6 mg/m3 in the cockpit. More research is needed, such as through air sampling during thermal runaway in simulated or in-field environments, for a more complete understanding of risks on an airplane and in other settings. The modeled concentrations span above the U.S. EPA 10-minute Acute Exposure Guideline Level-1 (AEGL-1) of 0.8 mg/m3, intended to protect against reversible irritation or discomfort. However, modeled concentrations fell below the 10-minute AEGL-2 of 78 mg/m3, intended to protect against more serious effects. Safety procedures such as reentry time calculation, storage and shipping procedures, and engineering controls should be considered by all employers whose employees come in contact with lithium ion batteries.