Quick Facts About EV Fires
- Electric vehicle fires did not burn hotter or last longer than gasoline vehicle fires in new full-scale testing.
- Researchers found ordinary water remains the preferred way for firefighters to control an EV fire.
- EV battery fires can continue through thermal runaway even after flames elsewhere in the vehicle are extinguished.
- Fire blankets can control cabin flames but may create additional hazards when an EV battery is burning.
Electric vehicle (EV) fires can produce dramatic images and present unique challenges for firefighters. But new research suggests EVs and gasoline-powered cars may have more in common when they burn than many drivers realize.
The Fire Safety Research Institute (FSRI), part of UL Research Institutes, burned 18 vehicles in controlled full-scale experiments to compare fire behavior and EV suppression methods. The 3-year project included three gasoline-powered vehicles and 15 EVs.
“Most of the vehicle is the same. It’s just really the battery that’s different,” said Adam Barowy, principal research engineer at FSRI and a co-author of the report.
EV Fires Didn’t Burn Hotter or Longer
Researchers found EV and internal-combustion vehicle fires were similar in peak fire size and time to burnout. The report found no evidence that EVs burned hotter or lasted longer than fires for conventional vehicles.
Much of a vehicle fire’s fuel comes from plastics, foam, upholstery, and other passenger-compartment materials that are largely the same regardless of powertrain.
“The peak fire size was pretty much the same,” Barowy said, adding that the unsuppressed fires all burned out within 80 minutes. “Largely, the fire behaviors overlap.”
EV fires are not identical, however. Once a battery enters thermal runaway — a chain reaction in which battery cells rapidly heat and fail — it can create hazards not found in a gasoline vehicle.
Water Still Works
FSRI found water was the most effective suppression agent tested. It quickly controlled the passenger-compartment fire, but large amounts of water generally could not stop thermal runaway inside the battery.
One reason is access.
“The battery is watertight. They have to design it this way,” Barowy said. Because the pack sits beneath the passenger compartment, “access is the primary problem.”
The report recommends controlling the vehicle fire and protecting nearby people and property while the involved battery completes thermal runaway. Adding the F-500 suppression agent tested by researchers did not improve performance compared with water alone.
Fire Blankets Aren’t a Simple Solution
FSRI found vehicle fire blankets could suppress passenger-compartment flames, but they could not stop thermal runaway in the battery.
Because thermal runaway does not depend on external oxygen, flammable gases can continue accumulating beneath a blanket. Under some conditions, those gases can create a flash-fire or explosion hazard, especially indoors or in confined spaces.
Barowy emphasized that researchers are not saying fire departments should never use blankets. Rather, firefighters need to understand the additional risks before deploying one.
EV Fires Still Have Unique Hazards
EV fires involving the battery produced elevated levels of nickel, manganese, cobalt, and particulate fluoride compared with gasoline vehicle fires. Battery reignition can also remain a concern after the initial fire is controlled.
Those issues primarily affect firefighters, tow operators, and others handling the vehicle afterward.
For drivers, Barowy’s advice is simple: Call 911, tell the dispatcher the vehicle is electric, don’t try to move it, and don’t attempt to fight the fire yourself.
“Protect yourself, back away, call 911, get the experts there going as soon as possible,” he said.
What the Study Doesn’t Tell Us
The research does not show whether EVs are more or less likely than gasoline vehicles to catch fire. The experiments examined what happens when vehicles burn and how firefighters can respond.
The EVs tested also used nickel manganese cobalt, or NMC, batteries. Lithium iron phosphate batteries were not included, nor were severe crashes, victim extrication, or thermal runaway without an external fire.
Still, the findings challenge a broader assumption about EVs: A burning electric vehicle isn’t necessarily a bigger or hotter fire simply because there’s a large battery underneath it.
As Barowy put it, “It’s not like a time bomb or something that’s going to go off. It’s a vehicle fire.”
