BY JESSE ROMAN
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This article is reprinted with permission from NFPA Journal, © 2024 NFPA.
The presence of LITHIUM-ION BATTERIES in home settings— owering everything from e-scooters to electric vehicles to energy storage systems—is expected to skyrocket in coming years and is forcing the fire service to rethink its response to residential fires. Research is underway to better understand how the batteries react in fire situations, and to help the fire service prepare for a rapidly emerging new hazard.
During a presentation in June at the NFPA Conference & Expo® in Las Vegas, UL research engineer Adam Barowy had plenty of material to keep his standing-room-only audience in rapt attention.
For the past few years, Barowy, along with a team of engineers from the UL Fire Safety Research Institute (FSRI) and UL Solutions R&D, have been heating up lithium-ion batteries—the type used in large-scale energy storage systems (ESS)—to the point of failure to see what kinds of reactions occur. The tests are videotaped for the team to analyze.
Spoiler: incident data demonstrates that, while failure events are unlikely, the consequences of those events can be severe without adequate protections. And those consequences are getting the attention of fire service leaders concerned about the coming wave of large lithium ion batteries used for powering omes, vehicles, ebikes, e-scooters, and more.
A typical video goes something like this: A single cell, bundled with a dozen or more identical cells around it, is purposefully sent into what’s known as thermal runaway, a chemical failure that causes heat to quickly build until the cell is almost incandescent, like a lump of iron just out of a blast furnace. The intense heat rapidly spreads to adjacent cells, which also go into thermal runaway and, in turn, trigger more cells to fail. Often, there is a loud pop when the cell casing fails, accompanied by a sizable puff of flammable, milky white smoke. As the pressure within each cell grows, more pops follow, each contributing more gas.
The gas, a mix of carbon dioxide, carbon monoxide, hydrogen, and hydrocarbon gases, can appear like smoke from a vent-limited fire. However, Barowy describes it to the fire service as “uber-smoke” for its comparatively high burning velocity and low minimum ignition energy. he gases coming directly from the battery are reactive enough that “it’s useful to think about an unignited thermal runaway like a propane gas leak,” he said.
An explosion hazard develops if this gas continues to accumulate without ignition. In one UL test, the enclosed test space filled with a thick, dangerous fog before igniting. When ignition occurs, the effect can be a sudden deflagration, generating pressures that sometimes send the heavy garage doors of the test space flying off their hinges, landing dozens of feet away. In other tests, the gases catch fire almost immediately and the flames grow with each successive pop, until there is a roiling inferno.
The point of showing these dramatic videos is not to imply that accidents involving large lithium-ion batteries happen all the time, Barowy said, or to suggest that product manufacturers aren’t interested in making their products safer. Failure events are in fact being mitigated by manufacturers, he said, and many prioritize proper engineering to reduce the frequency and severity of hazards—practices that so far have contributed to a demonstrated low failure rate in large lithium-ion batteries. The point of the videos is to illustrate the uniqueness of the hazard scenarios that can arise when incidents do happen. “And as the deployment of these systems increases, so will the number of incidents, as is the case with most consumer products,” he added. “We can certainly envision the fire service having to deal with this type of situation.”
Research is being conducted to better understand how large lithium-ion battery systems react during failure, and comes at a critical time for the fire service as it prepares for what could be a sea change in how we store and use electricity. Like the large batteries used for electric vehicles (EVs), energy storage systems for home applications are becoming cheaper and increasingly common around the world. These battery systems—flat, surfboardshaped appliances typically installed in garages—are used as a means to store the power generated by photovoltaic panels, as sources of backup power, and as a way to charge other lithium-ion powered devices, including EVs.
According to the renewable energy research firm Wood Mackenzie, there was a total of 600 megawatts of new residential energy storage capacity installed in homes in the U.S. in 2022, a 50 percent increase over the year before. The firm predicts that the annual residential installation of home batteries will exceed 2.7 gigawatts by 2027, about 4.5 times higher than the current rate of installation. That equates to roughly 135,000 new residential ESS systems being installed annually for the next three years. That aggressive growth rate—not to mention the millions of additional lithium-ion-powered consumer products showing up in residential garages each year—is not lost on the fire service. Aside from the FSRI tests, there have already been real-world incidents to grab their attention.
Research is being conducted to better understand ow large lithium-ion battery systems react during failure, and comes at a critical time for the fire service as it prepares for what could be a sea change in how we store and use electricity. Like the large batteries used for electric vehicles (EVs), energy storage systems for home applications are becoming cheaper and increasingly common around the world.
These battery systems—flat, surfboardshaped appliances typically installed in garages—are used as a means to store the power generated by photovoltaic panels, as sources of backup power, and as a way to charge other lithium-ion powered devices, including EVs.
According to the renewable energy research firm Wood Mackenzie, there was a total of 600 megawatts of new residential energy storage capacity installed in homes in the U.S. in 2022, a 50 percent increase over the year before.
"As the deployment of these energy storage systems increases, so will the number of incidents, as is the case with most consumer products. We can certainly envision the fire service having to deal with these types of situations"
The firm predicts that the annual residential installation of home batteries will exceed 2.7 gigawatts by 2027, about 4.5 times higher than the current rate of installation. That equates to roughly 135,000 new residential ESS systems being installed annually for the next three years.
That aggressive growth rate—not to mention the millions of additional lithium-ion-powered consumer products showing up in residential garages each year—is not lost on the fire service. Aside from the FSRI tests, there have already been real-world incidents to grab their attention.
Last April, a thermal runaway in the battery of an electric SUV in Erie, Colorado, resulted in a deflagration that blew the garage doors of a home 30 feet into the driveway, striking (but not injuring) a battalion chief standing outside. A similar event in Montreal in 2019 rocketed the garage doors at least 60 feet from a home, and in Germany a blast involving a residential ESS lifted the roof from the home and shattered the windows. No one was hurt in these incidents, but that’s not always the case. The most notorious battery incident to date occurred in 2019 in Surprise, Arizona, when a utility-owned energy storage system went into thermal runaway, resulting in an explosion that hospitalized four firefighters. One of them, a fire captain, was blown beneath a chain-link fence before coming to rest 75 feet from the ESS installation.
Although nothing as dramatic has happened during a residential ESS incident, fire service leaders fear that it could only be a matter of time unless solid tactical guidance is developed alongside training and updated prescriptive code requirements.
“The lithium-ion battery issue is coming at us like a steamroller coming down the road, because the financial and environmental pressures to adopt this technology are tremendous,” said Sean DeCrane, the director of health and safety operational services at the International Association of Fire Fighters (IAFF). “The fire service is not saying, ‘Stop, this can’t come to market!’ Instead, we need to be involved in the process to help steer that steamroller. Because at the end of the day the manufacturer gets to walk away when there is a failure— it’s the fire service that is going to be there to see it to its conclusion.”
The problem right now, said DeCrane, are all of the unknowns surrounding this hazard. “At the moment there are no hard-and-fast rules on how to respond to a residential lithium-ion incident,” he said in an interview. “What we have now are considerations based on the research, and those can be revised at a moment’s notice.”
"In this sequence, a lithium-ion battery mounted to the wall in a UL test facility begins to burn and combustible gases fill the room as more of the battery's cells ignite and explode. In some cases, as in the image at lower right, the gases ignite, resulting in a deflagration that destroys the test space."
NO EASY ANSWERS
Before concrete guidance on tactical response to residential ESS incidents can be developed, however, many important questions still need to be answered. One important detail that has vexed researchers so far is understanding the basics of when a lithium-ion battery in thermal runaway will catch fire, versus when it will experience a violent deflagration— or do nothing at all.
“The timing and severity of a battery gas explosion is so unpredictable, and this lack of consistency with ignition makes it difficult to talk in absolutes,” said DeCrane, who has worked closely with UL engineers on developing and interpreting the results of its live fire battery testing. “Adam and I have spent a lot of time talking about this. When we were doing the outdoor testing, we got back to the hotel one night and sat there eating a pizza, and Adam looked at me and said, ‘What’s wrong?’ And I said, ‘What the heck do we tell our members?’ Because for me personally, every time before we started a test I’d think ‘We’ve got a handle on this.’ But then we’d do another test, and we’d end up going, ‘Huh, okay—something different.’”
Barowy sums it up like this: “Even when we’ve tested the same product multiple times, sometimes it’ll ignite as soon as the runway starts. And sometimes it never ignites.”
Right now, the only certainty that DeCrane can offer the fire service is that “complacency can get you in a lot of trouble very quickly,” he said.
Nearly every part of the fire service response, from size-up to overhaul, proves challenging when it comes to events involving lithium-ion ESS. There are no requirements for placards on houses to inform fire crews that a lithiumion ESS r EV is located inside, making it difficult to know whether the hazard is present or not. When a fire crew does verify the presence of a residential ESS, its its response options are limited. As far as DeCrane knows, there are still no effective tools for firefighters to use to iagnose when a battery is in thermal runaway, whether it is involved in the fire, or what danger it poses. UL has presented research showing that standard thermal imaging devices cannot distinguish if the battery is involved in a room and contents fire, and gas meters have proven ineffective at differentiating smoke, battery gas, or a mixture of the two.
If firefighters do suspect a battery is in thermal runaway without active fire, their options are again limited. Water is the most effective known means for removing the heat that perpetuates thermal runaway propagation, but product enclosures almost universally prevent water ingress. In some cases, water may contribute to shortcircuiting and reignition at a later time. And the challenge is clear: FSRI testing and the Colorado incident both demonstrate that a significant explosion hazard may develop before any exterior that a significant explosion hazard may develop before any exterior indicators are evident. The best course of action at that point may be for firefighters to simply back off.
“Through testing we know that battery gases burn with a similar capacity to propane,” DeCrane told the audience at the crowded NFPA conference session. “Do I commit firefighters to a room if I think that room is filled with propane? Hell, no!” That’s why the safest approach for fire departments during incidents involving large lithiumion batteries may be to step back and remain cautious. But watching a structure burn or remaining idle while waiting for conditions to change, aren’t great options either, DeCrane admitted. Much is now happening behind the scenes at FSRI and elsewhere to provide more intelligence to fire officers on operational tactics that can be effective without putting firefighters at risk. That includes research on how firefighters can safely vent flammable gases to make a deflagration less likely. But this, too, is tricky.
Because the battery off-gases “ubermoke,” as Barowy calls it, cutting into a garage door is ill-advised because sparks can potentially ignite the gases and trigger a fire or even a deflagration. The common tactic of creating ventilation holes in the roof is also problematic. “I also wouldn’t want to put my firefighters on an engineered lightweight roof system above an explosive atmosphere,” DeCrane said. “So what’s the approach? Good question.”
Getting close enough to a structure to open windows or doors may also put firefighters at risk if a blast were to occur, but FSRI and the IAFF arelooking at this as possibly the best of a series of poor potential options. “Maybe we have a charged hand line ready, and if there’s an exterior access door, we approach it to vent gases that way. But we don’t necessarily want our members to interact with that garage door because we know from testing that that’s the weak point” during a blast, DeCrane said. The researchers plan on more tests and to take that information back to an advisory panel in the hopes that the group can come out with solid advice. But that could take time.
“From an IAFF perspective, we have 335,000 members out there. And when they look to us, they have to know, ‘OK, the IAFF has vetted this. We can take these recommendations and we can safely incorporate them,’” DeCrane said. “So we take this extremely seriously. We don’t want to start rolling out recommendations unless we’re very confident.”In the meantime, education and outreach are also needed so that more fire departments understand the risks of products powered by large lithium-ion batteries and the potential they have to seriously injure firefighters. NFPA has developed an array of resources that address these needs, including an online energy storage and photovoltaic systems training course designed for the fire service. (For more on NFPA training resources for ESS hazards, visit nfpa.org/ESS.)
"With all there is yet to learn about the technology, it¯s unlikely that research will catch up to the rate of energy storage system adoption anytime soon, but the ball is moving down the field« In the meantime, experts urge the fire service to remain vigilant and engaged."
The Fire Protection Research Foundation has also begun preliminary work to find funding for a project addressing residential ESS.
DeCrane, Barowy, and other experts say that the more organizations that are involved in trying to answer these thorny questions, the better. There’s no shortage of work to do, they say, even beyond firefighter response. For instance, overhaul after a lithium-ion incident ends also presents its own galaxy of questions and unique challenges because of the battery cells’ well-established propensity for reignition hours, days, or even weeks after an incident. This makes it imperative to find and gather every cell in any damaged lithium-ion battery to revent a return trip to the same address for a reignition. Digging through rubble for damaged, electrically charged battery parts requires special equipment and care, and disposal of the damaged material requires specialized wastemanagement procedures. Important questions also remain about how harmful lithium-ion off-gassing is to firefighters’ health and to the environment, and how to effectively clean exposed gear.
"In this sequence, a lithium-ion battery mounted to the wall in a UL test facility begins to burn, and combustible gases fill the room as more of the battery's cells ignite and explode, In some cases, as in the image at lower right, the gases ignite, resulting in a deflagration that destroys the test space."
With all there is left to know, it’s unlikely that the research will catch up to the rate of ESS adoption anytime soon, but the ball is moving down the field. As more and more ESS systems are installed across the world, DeCrane urges the fire service to remain vigilant and engaged.
“You have to be eager and open to educating yourselves, because the education isn’t going to be just dropped in your lap,” he said. “We’re providing a lot of information on the FSRI website (fsri.org). NFPA has been developing educational materials. The IAFF has a Department of Energy-funded project that’s mostly dedicated to developing educational material and getting it out to the membership. So look for that education, and ask questions. Make sure you’re getting information that is reliable and is truly tested, so that we can all understand what we’re starting to deal with.”
JESSE ROMAN is senior editor at NFPA Journal and host of The NFPA Podcast.
Is There A Battery In There?
For the fire service¥ the best way to fight a battery fire starts with knowing thereÉs a battery involved
One of the hardest but most important parts of dealing with a fire involving a large lithium-ion battery— or multiple batteries— is knowing that you’re dealing with some kind of energy storage system, said Sean DeCrane, the director of health and safety operational services at the International Association of Fire Fighters.
It sounds simple, but during a residential fire there is often no indication that there’s a large battery in the garage that is in a state of thermal runaway, spewing flammable gas. “These do off-gas a great deal, but there are scenarios where the wind’s blowing just right or the light’s shining just right or it’s night, where maybe you don’t even see that you’ve got a lot of flammable gas coming out of that garage,” DeCrane said.
The foolproof way of etermining if a battery is involved is asking the homeowner, he said. Beyond that, it’s making educated guesses based on clues like the presence of an electric vehicle in the driveway, or a photovoltaic nstallation on the roof. Fire crews can also look at the utility connection to thehouse to see if that signals anything unusual. Context and knowing your district is also important, De- Crane said.
“We talk to our firefighters all the time, independent of batteries, about knowing your running district. Know the type of construction, the type of occupancies, the types of hazards. This is no different,” he said. “When you’re going to work, your eyes should be open looking around at what’s being built.
What’s the affluency of your neighborhood? Are there photovoltaic systems installed? Are there energy storage systems installed? Are electric vehicles popular in your community? Do you have a lot of electric scooters? All of these things should raise your sense of that probability of a residential fire involving a large lithium-ion battery.”
The foolproof way of determining if a battery is involved in a residential fire is to ask the homeowner. Beyond that, it's making educated guesses based on clues, like the presence of an electric vehicle in the driveway"
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