E-bikes. E-scooters. E-motorcycles. Hoverboards. Electric delivery vehicles are parked in hallways and charging in spare bedrooms. The rise of lithium-ion battery-powered e-mobility devices is changing how people live — and it is changing the fire risk in residential buildings around the world.
These devices catch fire differently than anything fire protection professionals have dealt with before. They do not smolder and build slowly. They explode. In less than 60 seconds, an e-scooter undergoing what scientists call thermal runaway can take a room from normal to flashover — a total-room fire event that is unsurvivable.
The question the fire protection community has been asking is a fair one: Can residential fire sprinklers handle that?
Research from the Fire Safety Research Institute (FSRI), part of UL Research Institutes, answers that question clearly: Yes, they can.
What is Thermal Runaway, and Why is it so Dangerous?
Lithium-ion batteries (LIB) store a lot of energy in a small space. Under certain conditions — a bad charger, physical damage, a manufacturing defect, or simply age — the cells inside a battery can begin to overheat. As the temperature rises, chemical reactions inside the battery speed up. Those reactions create more heat, which creates more reactions. The process feeds itself in an accelerating loop.
Eventually, the battery releases a cloud of flammable gases. When those gases ignite — sometimes with explosive force — fire can fill a room in seconds.
In New York City alone, fires started by LIB-powered micro-mobility devices caused 267 fires, 150 injuries, and 18 deaths in a single year (2023). Similar patterns have been documented in London, Seoul, Sydney, and cities across Europe and Asia. In most cases, the fires happen in homes and apartments — exactly the kind of places where residential fire sprinklers are designed to protect people.
What the Research Actually Showed
Researchers at FSRI conducted a series of full-scale fire tests inside a purpose-built single-family home in Sharon Hill, Pennsylvania. A residential sprinkler system was designed and installed by the National Fire Sprinkler Association (NFSA) to meet NFPA 13D, the U.S. standard for sprinkler systems in homes.
The e-scooter used in the tests carried a 60-volt, 1.2 kilowatt-hour lithium-ion battery pack — the kind of battery found in many sit-on scooters sold around the world. Researchers triggered thermal runaway both by overcharging the battery and by direct heating.
Five experiments were conducted — four in closed bedrooms and one in an open living room.
In every single test, the sprinkler system worked.
Here is what happened:
- The sprinkler activated within 3 to 5 seconds of ignition in the bedroom tests, and within 5 seconds in the living room.
- In all five tests, flashovers never occurred.
- The fire was contained to the e-scooter itself. It did not spread to the bed, the sofa, or other furnishings in the room.
- Temperatures and gas concentrations outside the room of fire origin remained at levels where people could still escape.
For comparison, the same research team’s earlier work showed that an identical e-scooter — without sprinklers — drove a bedroom flashover in less than 60 seconds. The room temperatures exceeded 1,000°C (1,832°F). No one in that room would survive.
With sprinklers, the peak temperature in the room of origin was held to a fraction of that level. The hallway outside a closed bedroom door never exceeded 61°C (142°F) — warm, but survivable.
What This Means for Residential High-Rise Buildings
Residential high-rise buildings present a particular challenge. They are exactly the kind of occupancy where e-mobility devices are most commonly stored and charged — often inside apartments, near front doors, or in common corridors — and they are also the kind of occupancy where evacuation takes time.
A fire that reaches a flashover stage in 60 seconds on the 14th floor is a fundamentally different emergency than a fire that does the same thing in a detached home. Stairwells are longer. Elevators cannot be used. Other residents above and below the fire floor are at risk.
NFPA data show that homes with fire sprinklers have a civilian death rate 89% lower than homes without them. That statistic was developed based on conventional residential fires. The FSRI research suggests that advantage holds — and may be even more important — for the rapid, explosive fire growth caused by lithium-ion battery failures.
Several findings from the research are especially relevant for high-rise residential buildings:
Closed doors still matter. Even a hollow-core bedroom door provided meaningful protection to people on the other side. Occupants in adjacent units, corridors, and other floors had time to evacuate safely.
The sprinkler system activated before the fire reached its worst point. Because LIB fires grow so fast, there was concern that the fire might outpace sprinkler response. In practice, fast-response sprinklers were activated within seconds, containing the fire before it had a chance to spread.
The living room scenario activated four sprinklers simultaneously — far more than the system was designed to supply. Yet the system still controlled the fire. That is important in larger open-plan living spaces, which are increasingly common in modern high-rise residential design.
Toxic gases — not just heat — are a serious risk. The research measured carbon monoxide (CO) concentrations and calculated what scientists call the Fractional Effective Dose (FED). Essentially, how quickly the air becomes life-threatening. In the sprinklered bedroom tests, toxic conditions developed very rapidly inside the room of origin. Getting out of the room quickly matters enormously. The good news: beyond the closed door, conditions remained survivable for several minutes.
The Bottom Line for Building Owners, Developers, and Regulators
E-mobility devices are not going away. In many cities, they are the primary transportation for hundreds of thousands of residents. The fire risk they carry is real, well-documented, and growing.
The solution is not to ban the devices — it is to build and maintain the fire protection infrastructure that limits the damage when something goes wrong.
This research provides strong evidence that residential sprinkler systems, properly designed, installed, and maintained to current standards, can control e-scooter and e-mobility fires. They activate quickly enough. They suppress effectively enough. And they protect people outside the room of origin from both heat and toxic smoke.
For building owners and developers, this research makes a compelling case for:
- Ensuring that residential sprinkler systems are installed in all new residential high-rise construction.
- Verifying that existing systems are regularly inspected, tested, and maintained (ITM) in accordance with NFPA 25.
- Reviewing building policies on e-mobility device storage and charging — and pairing any restrictions with a clear commitment to fire protection infrastructure.
For regulators and code officials, the message is similar: the fire scenarios that sprinkler systems must handle are changing. The research community is doing its part to document that change. The codes and standards process must continue to evolve in response.
A Note on What Sprinklers Cannot Do
This research also confirms something important: sprinklers buy time. They are not a complete solution on their own.
Anyone in close proximity to an e-scooter during thermal runaway — in the same room, near the device — faces extreme danger in the seconds before the sprinkler activates. Plume temperatures near the burning scooter exceeded 800°C (1,472°F) in the experiments. That is immediately fatal.
Toxic gas concentrations in the room of origin can reach life-threatening levels within 9 seconds of ignition.
This means occupant behavior still matters enormously. Get out. Stay low. Close the door behind you. The data confirm that a closed door is a meaningful barrier. The well-known public safety message — “Close Before You Doze” — is backed by the same kind of science that supports this research.
Sprinklers give people the time they need to escape. They do not eliminate the need to escape.