As lithium-ion battery fires become more frequent, Juho Toukola, CSO of Latauspolku Oy, examines why fire safety strategies must move beyond prevention and address the consequences of thermal runaway
Lithium-ion batteries are everywhere. They power e-bike commutes, cordless tools on every construction site and robot mowers in groundskeeping fleets. Their numbers grow every year and so do the number of fires they cause. In January 2026, a DSV logistics terminal in Poland burned to the ground.
In Finland, a country of roughly 5.7 million people, two battery fires made national news within this spring. In Oulu in April 2026, a family of two adults and four children were forced to evacuate their home and were subsequently hospitalised, while neighbouring apartments suffered smoke damage.
In Espoo in May 2026, a tenant noticed an e-scooter battery beginning to overheat and did exactly what every safety guideline instructs: he moved to take it away from everything else. It exploded in his face and the fire spread to an e-bike battery beside it.
Apartment destroyed, building and other apartments suffered massive smoke damages. These are not exotic events anymore. More batteries mean more failures and a failing lithium-ion battery is unlike anything else in our buildings and workplaces. Once thermal runaway begins, there is no practical way for an ordinary person to put it out.
What happens when a lithium-ion battery fails
Thermal runaway is a self-accelerating chain reaction inside the battery cell. Heat generates more heat, cell by cell and the battery becomes its own fuel and its own oxygen source. This is why a battery fire behaves so differently from a bin fire. It reignites.
It ejects burning material. Cells can rupture violently, turning the battery into a source of projectiles as the Espoo tenant learned at close range. The fire itself is only part of the danger.
A burning lithium-ion battery releases a cocktail of toxic gases, most notably hydrogen fluoride. It is dangerous even at low concentrations. In large quantities it penetrates skin and tissue, but even in the light smoke we see before visible ignition it attacks the lungs and can cause severe injury to people who never see a flame. The Oulu family were hospitalised not because flames reached them, but because smoke and gas did. This combination of unstoppable fire, violent failure and toxic gas is what makes the lithium-ion problem categorically different from the fire risks our buildings were designed for.
Three pillars of lithium-ion battery fire safety, two of which fail at the critical moment
Society currently governs this risk with three tools: guidelines, restrictions and technology. It is worth being honest about what each one can and cannot do.
Guidelines are genuinely valuable. Charge with the original charger, inspect batteries for damage, do not charge unattended, do not charge near exits. Followed properly, they greatly reduce the already small probability of a fire.
But probability reduction is all they do. Guidelines do not stop thermal runaway once it begins and they quietly assume a level of supervision that does not exist in real life. The standard instruction to “supervise charging” asks a resident to watch a battery for seven hours or a logistics operator to assign a human to every charging shelf.
Nobody does this. Everybody knows nobody does this. And as Espoo showed, even the person who notices the problem early and follows the guidance to the letter can end up in the path of the failure. Restrictions are the newer instrument and they deserve more scrutiny than they get.
Housing companies and facility operators across Europe are responding to the risk by banning e-bike and e-scooter charging indoors. On paper, the risk disappears. In practice, it goes underground.
People do not stop charging the device they depend on for their commute. They charge it in their apartment, behind a closed door, where no policy reaches and no detection exists. A prohibited risk that everyone quietly takes is not a managed risk.
It is a denied one and it surfaces exactly the way the Espoo and Oulu fires did: inside homes, where people live and sleep.
A wild west of lithium-ion battery fires solutions
Walk through any fire safety exhibition and you will find an expanding catalogue of products marketed against battery fires. Many of them solve a fraction of the problem and leave the rest untouched.
Fire pouches, blankets and battery tarps can be useful for small consumer cells, but an e-mobility battery pack in full thermal runaway generates enough sustained energy to defeat most of them in seconds rather than contain them for minutes.
Specialised battery extinguishers exist but using one effectively means approaching a device that is ejecting flame, gas and potentially projectiles. For a trained responder in protective equipment with self-contained breathing apparatus, that is workable.
For a resident, a warehouse worker or a night-shift caretaker, in normal clothing it is not a realistic instruction. Passive fireproof cabinets are a step up.
They contain the fire and protect the surrounding space from flame spread. But containment is not suppression. The reaction continues inside and the toxic gases still need somewhere to go.
The effect to people problem remains unsolved. Active suppression systems based on aerosols go further and attempt to interrupt the fire. The difficulty is that aerosols suppress visible flame without reliably stopping the chain reaction underneath it and testing has shown that suppressing the flame while the cells continue venting flammable gas can create explosive conditions. Slowing the reaction is not the same as ending it.
Stop arguing probability. Engineer for consequence of lithium-ion battery fires
The uncomfortable truth is that these fires cannot be prevented. As long as lithium-ion chemistry surrounds us, a small number of failures is a statistical certainty. The meaningful question is not ‘how to reach zero probability’, because we cannot.
It is what happens in the building when the failure occurs. Research within Finland’s national LION project points to a clear answer: water immersion.
