Assessment of Hazardous Substance Exposure During Electric Vehicle Fires

Internal combustion engine vehicles and electric vehicles share many similarities in the event of a vehicle fire but also differ in certain aspects. While both vehicle types release pollutants typical of vehicle fires, fires involving electric vehicles also emit battery-specific emissions. To investigate hazardous-substance exposure of emergency responders, two fire tests were carried out on identical electric vehicles. In each test, one battery cell was mechanically short-circuited, resulting in thermal runaway and propagation within the battery. Gas and time-resolved aerosol measurements, wipe samples, extinguishing agent samples, and urine samples were analyzed. A primary finding was the pronounced variability between the two fire events: despite comparable test conditions, the two vehicle fires exhibited markedly different development patterns, highlighting the inherent variability of electric vehicle fire behavior. Wipe samples showed increased metal concentrations after the tests, with maximum post-extinguishing surface concentrations of 7.4 mg/m2 nickel, 17.45 mg/m2 cobalt, and 14.25 mg/m2 lithium. Extinguishing agent samples showed increased concentrations of inorganic contaminants and polycyclic aromatic hydrocarbons. Urine samples showed no indication of a systematic increase in creatinine-adjusted metal concentrations among protected participants. Toxic gases were released immediately after cell short-circuiting, with hydrogen fluoride, hydrogen cyanide, and acetylene reaching approximately 500 ppm before visible flames occurred. Aerosol measurements identified transiently elevated particle number concentrations in the exterior near-field environment and, in one test, inside the passenger compartment, where a shift towards smaller particle diameters was observed. The findings demonstrate multiple responder-relevant exposure pathways and substantial variability in electric vehicle fire events.