Adam Barowy, Principal Research Engineer at UL Research Institutes’ Fire Safety Research Institute, shares the findings from the Institute’s research into lithium-ion batteries and electric vehicle (EV) fires and details how fire crews can best prepare to combat these incidents
As electric vehicle (EV) adoption continues to grow, fire and rescue services are increasingly encountering incidents involving EVs. But how different are EV fires from those involving conventional petrol or diesel vehicles, and what does this mean for firefighters on the ground?
UL Research Institutes’ Fire Safety Research Institute has been conducting extensive research into EV fire behaviour, suppression tactics, and exposure risks for several years. The Innovation Platform spoke with Adam Barowy, Principal Research Engineer at the Fire Safety Research Institute, to learn what implications the research findings could have for both fire service professionals and EV owners.
How has your research helped to improve understanding around battery and electric vehicle fires?
Like much of what we do at UL Research Institutes’ Fire Safety Research Institute, our research into lithium-ion batteries and electric vehicle fires began because the fire service was responding to more and more incidents involving EVs. It was really no surprise that, as EV adoption increased, incidents involving EVs increased too. Our stakeholders in the fire service brought us questions about how to suppress fires that appeared at times to behave differently from those involving an internal combustion engine vehicle (ICEV).
Those differences and concerns included prolonged burning, resistance to extinguishment, reignition even days or weeks later, toxic and flammable gas release, flame jetting, and explosion or deflagration hazards. Several high-profile incidents contributed to the perception that EV fire behaviour was drastically different from what firefighters were used to encountering in ICEV incidents.
At the same time, we were also learning about a wide range of response tactics for EV fires – everything from using large amounts of water to cool the battery, to letting the battery burn out, to submerging the entire vehicle in a large container of water, along with specialised tools and tactics that haven’t been fully evaluated for efficacy or practicality.
Ultimately, in collaboration with our fire service stakeholders and other partners, our team set out to answer the following research questions:
- Do EV fires grow faster, bigger, or last longer than an ICEV?
- What is the chemical exposure to firefighters and the public resulting from EV fires?
- How effective are standard firefighting equipment and vehicle firefighting tactics for suppressing an EV fire? Can existing equipment be used more effectively?
- Can fire blankets or water additives increase firefighting effectiveness?
- What guidance can be developed for firefighters to improve safety and efficacy of EV firefighting?
Our three-year study began by examining EV fire behaviour and comparing it to ICEV fire behaviour, and then moved on to suppression tactics. We conducted full-scale burns of 18 vehicles, representing the most popular models by sales volume, including nine burns without any fire suppression. The subsequent nine burns looked at common suppression tactics, including water only, EV fire blankets and water with an added suppression agent. During the suppression tests, we allowed the fires to grow for six minutes to simulate the typical fire response time in North America. All vehicles had a full fuel tank or fully charged battery.
This research is helping to improve our understanding of how EV fires burn, how they compare to their ICE counterparts, and what tactics can help the fire service manage this new source of fuel on the fireground.
What have been the major findings from your research so far?
The key takeaways from our research are to:
- Expect similar fire behaviour and hazards from EVs and gas vehicles.
- Use water to control EV fires and reduce exposure.
- Use fire blankets with caution.
- Remain in full PPE and SCBA throughout the incident.
Our data from the free-burn experiments showed that EV and ICEV fires demonstrated similar fire growth rate, peak fire size, and fire duration. Unlike gas vehicles, we observed jets of flame that emanated from the battery in a minority of experiments, but the fire spread risk of these jets is small compared to any type of vehicle passenger cabin fire. I think this is particularly important given the perception, as I mentioned before, that fire behaviour is dramatically different in the different vehicles.
This is because the cabin – containing plastics, foam, and ordinary combustibles – is the biggest fuel driver in vehicle fires, and cabin design is very similar between EVs and ICEVs. In the free-burn tests without intervention, incidents concluded within 90 minutes for both types of vehicles.
We also found that water effectively suppressed the cabin fire and controlled battery flaming while the battery burned itself out. Water can also be applied to nearby exposures to protect them. In all of our tests, we weren’t able to stop thermal runaway in the battery once it started.
Because of the way battery enclosures are built in EVs, water can’t reach the battery and therefore using large amounts of water to cool the battery and interrupt thermal runaway is ineffective. Our tests also found that an added suppression agent was no more impactful than water, since neither can reach the burning cells inside the battery.
For fire departments, this is good news. They are generally able to meet the hazards of EV fires with tactics they already know and have practiced, and they don’t need specialised tools that require additional training or expense. While we don’t yet understand how many EV fires the United States fire service is facing on an annual basis or how those incidents unfold, research from other locations can be instructive. Data gathered by the Dutch fire service has indicated that the majority of EV fire incidents don’t involve the battery at all, underscoring the use of water to control the incident.
As we evaluated firefighting tactics, we also looked at the efficacy of EV fire blankets – one of the more popular suppression methods in use today. We found that EV fire blankets can control vehicle flaming and put out the cabin fire, but that thermal runaway in the battery pack will continue. Our team observed an explosion hazard if the flammable gases accumulate under the blanket or if the fire blanket is used in a confined operating environment like a parking garage.
Throughout all of this research, we also measured the exposure hazards associated with these fires – the smoke, suppression runoff water, and contaminated firefighting turnout gear. All vehicle types emit hazardous smoke, but we did see elevated concentrations of metals and particulate fluoride associated with the battery fire. Considering these exposures with the potential for sudden and rapid reignitions, firefighters need to remain in full personal protective equipment and self-contained breathing apparatus throughout the incident. The full impact on human health is not fully known, but contaminants from all vehicle fires are known to have negative health effects.
Based on the findings of your research, how can fire service providers adapt their response to EV fires?
Firefighters will need to make adaptations to their strategies and tactics, but life safety should continue to be prioritised, followed by control of the cabin fire. After the cabin fire is suppressed, water can be used to prevent the cabin fire from reigniting while the battery burns itself out. Following the incident, first responders need to work with second responders – such as tow operators – to understand and anticipate reignition. We recommend that the fire service escort the tow truck with a suppression unit in case of reignition.
At the end of the day, first responders can and should treat EVs and lithium-ion batteries as a fuel like any other. Once they understand how the fuel behaves, they can be prepared to respond to incidents of all types.
Do you have any recommendations for EV owners when it comes to fire safety?
Generally, EVs are going to be safe. They have been tested against rigorous safety standards. And for that very reason, our work is focused on helping firefighters respond to incidents if they do happen.
EV owners should pay attention to the manufacturer’s instructions and charging recommendations. If they are involved in an accident, they should have the battery checked for damage that could lead to a fire.
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