Can a fire blanket cause an explosion in an EV fire?
Flammable gases can build up under a fire blanket on a burning EV. Here is what makes them dangerous, and how correct deployment prevents it.
Yes. When an EV battery goes into thermal runaway, it releases flammable gases that can build up under a fire blanket. If oxygen gets in and the gas ignites, the result can be a deflagration.
Water makes the risk worse, because water on a hot, damaged battery produces more hydrogen. That is why Bridgehill's procedure is clear: no water or other liquids under the blanket, no lifting, and removal only by trained firefighters once the blanket's surface temperature matches its surroundings.
What happens under the blanket?
A fire blanket contains an EV fire. It can help slow thermal runaway, but it does not stop it. The battery event continues under the blanket until it has run its course.
During thermal runaway, the battery gives off flammable gases, including hydrogen, carbon monoxide and light hydrocarbons. These gases can build up under any cover, and that risk should never be downplayed.
But gas alone does not cause a deflagration. It takes three things:
- Fuel: flammable gas from the battery
- Oxygen: enough to bring the mixture into its flammable range
- Ignition: a heat source, which a battery in thermal runaway can supply
A properly deployed blanket cuts off the oxygen. That is why it has to stay in place, undisturbed.
What is a deflagration? A rapid combustion event that moves slower than the speed of sound. It can range from a mild pressure pulse to a violent blast, and it can happen in any EV fire where hydrogen builds up and then meets oxygen and an ignition source, whether or not a blanket is used.
Why is water under the blanket dangerous?
When water reaches a hot, damaged battery, hydrogen production speeds up. Under a blanket, that hydrogen has nowhere to go.
A lithium-ion battery normally contains lithium ions, not lithium metal. Above about 390°F (200°C), the protective layer on the anode and the graphite structure break down, and reactive metallic lithium can form. Metallic lithium reacts with water and releases hydrogen quickly.
The research summarized in Bridgehill's Global Fire Safety Notice shows hydrogen levels rising fast during water exposure and reaching explosive concentrations in confined spaces within minutes. Lift the blanket at that point, and oxygen enters a space that is already full of fuel.
This is not unique to fire blankets. It is basic lithium-ion chemistry, and the same thing can happen in any confined space where water meets damaged battery cells, such as a garage or a ferry deck.
What happened in Stryn, Norway?
A 2025 incident in Stryn, Norway, shows what can happen when water is applied under a fire blanket.
According to the Norwegian fire service magazine Brann & Redning, the Tesla was already fully involved when firefighters arrived. It was the department's first EV fire. Crews deployed a fire blanket and then, unable to reach underneath the car, ran two hose lines under the blanket to cool it. While cooling was underway, a powerful explosion tore the blanket apart and left car parts 23 to 26 feet (7 to 8 meters) away.
The crew was making decisions under pressure at its first EV fire. But the sequence matches the mechanism described above: water under a cover, on a battery in thermal runaway, in the same space where the gas is building up.
Bridgehill responded in the same article. Founder and CEO Frank Brubakken said water has never been part of the recommended procedure. After the incident, Bridgehill sent a notice on correct use to fire authorities and distributors in all of its markets.
Why not just cool the battery?
Cooling and containment are two different tactics with different goals. Putting water under a blanket combines the risks of both.
In Bridgehill's webinar Beyond the Flames, Dalan Zartman, CEO of the Energy Security Agency (ESA) and a fire service veteran of more than 25 years, describes it as a choice. Once life safety is addressed, crews should decide whether the main threat is the fire, the vapor or the battery damage. Letting the vehicle burn, suppressing the fire and containing it with a blanket can each be the right call.
When people nearby are at risk from the vapor, water can make things worse:
- Denser vapor plume. Water knocks down the flames, but without combustion, the toxic vapor gets denser and spreads farther. In Zartman's example, an EV is burning near a playground full of children. In that situation, he would contain the vapor with a blanket instead of suppressing the fire.
- HF travels farther. Hydrogen fluoride binds to steam and fine water droplets. Research from RISE Research Institutes of Sweden shows that this can carry HF farther through the smoke plume.
- Contaminated runoff. Water that flows over a burning EV picks up metals, fluorides and electrolyte residue and carries them into drains and soil.
- Stranded energy. Cooling can reduce visible activity while significant energy remains in the battery. That creates a risk of reignition later, during recovery, transport or storage.
Water-based suppression is still essential in many fire scenarios. The key is to choose one tactic on purpose rather than mix the two. Zartman calls fire blankets one of the safest interventions crews can use on a vehicle.
Watch the discussion. In the on-demand webinar Beyond the Flames, Zartman covers how to choose a tactic in Containment vs. Suppression (41:50), vapor and off-gassing in The Hidden Hazard (22:20) and correct blanket use in Fire Blankets in Practice (52:23).
Frequently asked questions
Should firefighters cool the battery under a fire blanket?
No. Water on a hot, damaged battery speeds up hydrogen production, and the blanket traps that hydrogen. If cooling is the chosen tactic, use it instead of a blanket, not underneath one.
Can the blanket be lifted to check on the vehicle?
No. Lifting it lets oxygen into a space that may already contain flammable gas. Monitor temperature and gas levels from outside instead.
When is it safe to remove the blanket?
Removal is for trained firefighters only. The blanket should come off only when its surface temperature matches the surrounding temperature. Because the battery can still reignite, Bridgehill recommends keeping the blanket on during transport and at the salvage yard for as long as it takes.
What caused the explosion in Stryn?
The blanket itself did not explode. Gas that had built up underneath it ignited. In Stryn, crews applied water under the blanket with two hose lines before the deflagration, which is outside the recommended procedure.
Are fire blankets safe to use on EV fires?
When used according to the procedure, a fire blanket contains flames, smoke and toxic vapor within minutes and keeps the fire from spreading to nearby vehicles and buildings. Fire service expert Dalan Zartman calls it one of the safest interventions crews can use on a vehicle.
Sources and further reading
- Global Fire Safety Notice: water risks, hydrogen buildup and correct use, with the full technical report
- Beyond the Flames: EV fire webinar with Dalan Zartman: tactic selection, toxic vapor and reignition, on demand
- Brann & Redning: Eksplosjon etter bruk av brannteppe (June 23, 2025, in Norwegian)
Related articles
