Home battery system fires create gasses 'close to propane,' danger of explosions

The growth of home battery systems is presenting a new danger for firefighters and homeowners. When the batteries overheat, they produce explosive gasses, such as hydrogen. If the gasses are ignited, such as when water contacts electricity and causes a spark, the building can explode. As more homes install battery systems, the problem is growing.

Multiple incidents

A new study by the International Association of Fire Fighters (IAFF) and UL Solutions shows incidents happening around the world where homes were destroyed and people were injured from malfunctioning battery systems.

In Erie, Colorado, firefighters responded to a structure fire on the morning of April 11, according to the study. There was no smoke seen when crews arrived, but crews searched the home and found smoke coming from a second garage where a Jeep Wrangler 4XE hybrid was parked.

Hybrid vehicles contain a gas-powered engine that can charge a battery. The smoke inside the garage was dense, and when firefighters applied water to the vehicle, an explosion blasted the garage door 30 feet into the yard. The garage door hit a first responder in the head, but his helmet protected him. Fortunately, no one was injured.

A woman in Sanbornton, New Hampshire installed a battery system built from three repurposed batteries from Chevy Volt cars in her home's mechanical room. On Dec. 17, 2022, the woman heard a “popping” sound. When she went to investigate, she found the battery system was “bubbling over.” When she returned with a fan, flames were coming from the battery and crawling up to the ceiling. The woman was injured, and the fire caused extensive damage to her home, according to the study.

On Oct. 2, 2019 a fire broke out in a "concrete bunker" in Brown’s Canyon, Colorado, according to the study. The bunker contained a wind and solar system, which was supported with batteries placed at the back of the bunker.

No one was injured in that incident, either, but in 2019, four firefighters were severely injured in Arizona when a fire from yet another battery system caused an explosion.

Where there’s smoke

In the United States, the number of residential energy storage systems (ESS) in operation has grown considerably in the past several years, according to the IAFF/UL study, from 13 megawatts in power capacity in 2017 to 310 megawatts in 2021. Global figures show similar increases in Europe, Canada and Australia. The largest increase is in Germany.

There's no hard data on how many homes in the U.S. contain lithium-ion battery systems, but one 2019 survey found that more than 21% of homes in the U.S. and Canada had home energy storage systems paired up with solar panels.



Lithium-ion batteries can malfunction and cause what’s called “thermal runaway,” where the battery produces more heat than it can dissipate.

When firefighters approach a house fire caused by a burning battery system, they aren’t always able to tell that the fire is coming from a lithium-ion battery. “The biggest challenge is understanding the presence of the hazard,” Sean Decrane, director of health and safety operational services for the IAFF, told Just The News.

There aren’t any requirements that a placard be placed on the exterior of a home warning that a battery system is in operation. “The National Association of Homebuilders really doesn’t want their homes to look like a NASCAR, with an identification for every hazard,” Decrane said.

Firefighters instead have to look for visual clues that they’re encountering a battery-system fire. A key indicator, Decrane said, is a “whitish type of smoke.” However, lithium-ion batteries are housed inside products, and when the other materials, such as plastics, burn, they produce dark smoke that masks the indicators of a battery fire.

Close to propane

What the study determined, Decrane said, is that the biggest hazard for firefighters is the explosion hazard. Depending on the battery's composition, the vapors produced can be as much as 70% hydrogen. Carbon monoxide, which is not just toxic but flammable, can occur in concentrations as much as 35%.

“We’re dealing with something that has properties very close to propane,” Decane said.

With a battery fire, he explained, the gasses are accumulating inside a compartment, and the battery also provides an ignition source. “Once they go through failure,” Decane said, “many times they start to throw sparks, and with the properties of the gas, that’s all the energy it needs to ignite.”

Decane said that due to a lack of funding for the study project, the IAFF and UL Solutions weren’t able to determine what various types of suppression methods for fighting the fires are best. The IAFF is hoping to do a follow-up project with the Department of Energy, Decane said, so they can start studying the options closely. “Sitting back and doing nothing in a single family home, especially if the occupants are home, really is not an option,” he said.

In lieu of such a study, Decane said the IAFF is looking at tactical considerations for its members. These include whether firefighters should break a window or open an overhead door to vent the gasses if a battery fire is suspected. “We don’t want them using a power saw. We don’t want them using striking tools, because those are ignition sources,” Decane said.

The best thing for firefighters is when there is an actual fire and not just the smoke.

“We have a saying. ‘If it’s on fire, relax, because it’s consuming those gasses,’” Decane said.

Decane said the fires can be prevented if owners of ESSs make sure the systems are installed and tested properly according to the appropriate standards. The standard for testing battery systems is UL9540, Decane said, and they should be installed by a licensed electrician according to the NFPA 855 standard.

Decane also said it’s important to not damage the batteries and recognize the warning signs of a battery system that’s malfunctioning. “If you start to see a battery that’s leaking, if you hear popping noises, if you smell a strange smell — they have a very distinct smell — we want you to call 911 right away and leave the house,” he said.