UL Research Institutes’ Fire Safety Research Institute has released a new evidence-based report designed to help firefighters better understand electric vehicle fires and the tactics available for safe incident response.
The report, ‘Full-Scale Electric Vehicle Fire Experiments and Recommendations for Fire Incident Response’, is based on full-scale burns of 18 vehicles and examines how EV fires compare with internal combustion engine vehicle fires, as well as how common suppression methods perform once a battery fire is involved.
Researchers conducted nine free-burn experiments without fire suppression, followed by nine additional EV fire tests to evaluate water, EV fire blankets, and water used with an added suppression agent. All EVs were fully charged before battery fires were initiated with a propane burner and allowed to develop for six minutes before suppression began, reflecting standard fire response time in North America.
“Lithium-ion battery-powered devices and EVs are already changing how we move, communicate, and enjoy our leisure time,” said Adam Barowy, principal research engineer for the Fire Safety Research Institute. “This research moves us closer to understanding how batteries change the fire environment and helps equip first responders to adequately address fires involving this new source of fuel. Our findings demonstrate that when it comes to EVs, first responders can effectively manage the hazard with familiar tools and tactics.”
The free-burn experiments found that EV and internal combustion engine vehicle fires were similar in fire growth rate, peak fire size, and overall fire duration. EVs released more total energy on average, which researchers attributed to greater vehicle mass.
For most EV fire incidents, the report says water can be used to suppress the cabin fire, limit exposures, and control flaming from thermal runaway while the battery burns itself out. None of the tested suppression techniques stopped thermal runaway once it had started, and an added suppression agent was no more effective than water alone.
Direct battery extinguishment or cooling is not recommended because vehicle construction prevents crews from effectively reaching the battery pack.
Researchers found that EV fire blankets can help control vehicle flaming, but may create an explosion hazard if flammable gases accumulate beneath the blanket or in a confined operating environment. The report recommends that blankets should not be repositioned once deployed and should not be used indoors or in confined spaces because of deflagration risk.
The report states that firefighters should remain in full personal protective equipment and self-contained breathing apparatus throughout the incident, including overhaul, due to persistent toxic exposure and reignition risk. Researchers found elevated concentrations of metals and particulate fluoride associated with battery fires in smoke, suppression runoff water, and contaminated turnout gear.
The full report also includes tactical considerations for size-up, exposure hazards, suppression, and overhaul. FSRI has developed an EV Fire Tactical Decision Aid to help firefighters analyze conditions and make safer decisions on the fireground, with the findings set to inform a forthcoming EV firefighting course in the Fire Safety Academy.
