Lithium-ion battery fire

A Lithium-ion battery fire is a fire involving the cells, electrolyte, packaging or surrounding materials of a lithium-ion battery or battery pack. It can be driven or sustained by thermal runaway, a failure mechanism that heats the cell and can propagate to neighbouring cells. Flammable gases, toxic combustion products, re-ignition and difficult access to the cells make these fires different from many ordinary combustible-material fires.

Battery packs are often sealed to protect them from moisture and dirt, which also makes direct cooling of the cells difficult. Flame extinction alone may not stop the underlying reactions, so repeated ignition can occur. Continued cooling, temperature monitoring and management of contaminated water and residue are therefore part of the response.

These fires can occur in vehicles, energy-storage installations and other equipment, but their development depends on cell type, state of charge, packaging and installation. Evidence from electric-vehicle studies should not be applied unchanged to every stationary system. The particular battery, enclosure and fire scenario must be assessed.

Thermal runaway and initiation

Thermal runaway is a failure mechanism that causes self-heating in a battery or cell and can result in fire. Each battery pack has a safety window, and exceeding it can lead to further heating. The reported onset range of 70 to 250 °C depends on battery type and is not a universal ignition temperature.

The mechanism can begin with design or manufacturing errors involving electrodes, separators, electrolyte or related processes. External heat, misuse, collision damage and charging faults can also contribute. A battery management system is intended to monitor abnormalities and intervene, but its presence does not remove every failure path.

The battery management system can support active cooling, stop charging or disconnect the pack when threshold conditions are detected. Its functions depend on the condition of the system and the fault being experienced. NIPV describes fail-safe deactivation for its discussed electric-vehicle packs, not as a guarantee for every battery system.

Ageing changes battery behaviour. Increased internal resistance can increase heating, while a lower maximum state of charge can reduce the intensity and gas production of a later thermal runaway. Those effects should not be reduced to a simple claim that every older battery is either more or less dangerous.

A Battery energy storage system can contain many cells whose arrangement, monitoring and enclosure affect propagation and cooling. The supplied NIPV source addresses electric-vehicle packs rather than providing a complete stationary-storage design standard. No universal stationary-installation rule is therefore stated here.

Gas release and propagation

A cell undergoing thermal runaway can release flammable gases as it heats. Those gases may ignite if sufficient oxygen and a suitable ignition condition are present. If gases accumulate in a confined or poorly ventilated space, they can produce a flammable or explosive mixture.

The heat from one cell can raise the temperature of adjacent cells and cause a chain reaction. The geometry of the pack and the ease of heat transfer influence that propagation. A fire involving one cell can therefore develop into a much larger battery-pack event.

Pressure can build in a pouch, cartridge or other enclosure and release gases if the enclosure or pressure valve fails. Mechanical damage can also eject burning parts and fragments from the pack. Those hazards differ from a fire that spreads only by ordinary surface flame.

Unignited gas does not make the situation safe. Continued degassing can create a cloud that later ignites, and an explosion can occur when the mixture and ignition conditions are suitable. Assessment must therefore include gas transport, ventilation and the timing of ignition.

An Electric vehicle fire can involve the battery pack, passenger compartment, charging equipment or an external fire exposing the vehicle. NIPV presents separate scenarios for a pack fire, radiation exposure from another vehicle and several packs burning. Those scenarios have different prevention and suppression requirements.

Fire development and re-ignition

Battery-pack fire development can differ from a liquid-fuel vehicle fire. NIPV describes a slower initial heating period followed by rapid development when thermal runaway occurs. The source compares the pack with hydrocarbon-fuel fire behaviour, not with every possible vehicle interior fire.

The source reports a conventional passenger-car fire of just over half an hour with about 5 MW after 10 to 15 minutes, and an electric-vehicle burnout of about 90 minutes without intervention. These are study-specific examples, not universal fire curves. Vehicle materials, battery condition and ventilation can change the outcome.

Re-ignition is a defining concern in many battery-pack scenarios. The reactions can continue after visible flames are suppressed, releasing gases that ignite again. NIPV reports re-ignition for several hours after the start in the cited study, which requires a longer assessment than initial flame knockdown.

Continuous temperature monitoring helps identify renewed heating and the need for continued cooling. Extinguishing whenever the pack reignites and applying continuous cooling are different operational choices. Both require sustained attention to the battery's temperature and remaining energy.

The fire can spread through vehicles to other cars and structures. Radiant heat from an adjacent fire can initiate thermal runaway in a pack that was not the original ignition source. Prevention and suppression must therefore consider both internal failure and external fire exposure.

Toxic and corrosive products

Fire toxicity includes the effects of gases and other products released by the cells, electrolyte, packaging and surrounding plastics. NIPV lists methane, carbon monoxide, carbon dioxide, hydrogen, hydrogen fluoride and hydrogen chloride among the products in its reviewed battery fires. The actual mixture depends on the battery and the fire.

Hydrogen fluoride is a particular concern in the cited vehicle research. NIPV reports a source estimate of about 20 to 200 mg HF per Wh, implying 2 to 20 kg for a 100 kWh pack depending on state of charge. Another cited comparison found about 1.8 times as much HF for electric vehicles as for conventional vehicles.

Those numbers belong to the cited tests and assumptions and must not be used as a universal emission factor. Battery chemistry, state of charge and test arrangement affect releases. The report itself emphasises the differences between studies and the uncertainties in those results.

HF is reactive and can bind to other substances and particles, forming deposits on floors, walls and ceilings. NIPV reports that this reduced airborne HF concentration in the cited work but increased contamination of firefighting clothing. Deposition therefore changes rather than eliminates the hazard.

Combustion products can spread into stairwells and escape routes through open doors or building openings. Location and ventilation affect where exposure occurs. The safety assessment must include smoke movement and people who take longer to leave, not only firefighters at the battery.

Suppression and cooling

Putting out visible flames is different from stopping thermal runaway. The battery's closed construction can prevent water from reaching the cells directly, so surface application may not stop the underlying reactions. NIPV describes prolonged cooling with substantial water as necessary for control in its studied scenarios.

Water can enter the pack only where the design provides access or where another method is used. NIPV describes immersion of the vehicle or battery pack as the currently successful approach in its cited fire-service guidance. Effectiveness depends on water reaching the affected cells and on continued monitoring afterwards.

Fire classes can guide initial agent selection, but a battery fire does not fit every assumption behind an ordinary solid or electrical-equipment label. Chemical reactions, sealed packaging, high voltage, gas release and re-ignition must also be assessed. Class selection cannot replace mechanism-specific evidence.

Sprinklers and water mist can reduce the probability of spread to adjacent structures and vehicles, but NIPV says they cannot necessarily extinguish the pack fire. Further research is needed on which systems best control different electric-vehicle scenarios. Their effect should not be equated with stopping thermal runaway.

Covering a vehicle in foam is not supported as a useful method in the cited NIPV discussion because re-ignition can occur under the foam, even with limited oxygen. That is specific evidence about the battery mechanism, not a general claim that foam has no other role in the incident.

Firefighting and salvage

Firefighting assessment must include explosions, toxic gases, high voltage, structure stability and uncertain fire development. NIPV identifies those factors as increasing the risks and uncertainties of a repressive attack. The presence of a battery also extends the period for which cooling and monitoring may be required.

The attack location and cooling capacity affect which tactics are possible. NIPV's principles ask whether the seat of fire is known, whether it can be reached from outside and whether sufficient cooling capacity exists. The answers determine whether an offensive exterior attack is possible.

NIPV gives low-pressure guidance of 450 litres per minute generally sufficient for a heat-release rate up to 10 MW and high-pressure guidance of 125 litres per minute for up to 2.5 MW. These are source-specific rules of thumb, not universal cooling guarantees for battery packs. The report separately stresses prolonged cooling and access to the cells.

Salvage planning should begin early. A vehicle may need to be removed to a suitable container or tank where cooling can continue until thermal runaway stops. The capabilities of the salvage company and the access conditions in the car park can limit that option.

Firefighting clothing and equipment can become contaminated by HF and other products. NIPV calls for decontamination in its electric-vehicle discussion and notes that this differs from conventional-vehicle incidents. Protective arrangements must address both airborne and deposited contamination.

Prevention, detection and management

Prevention includes battery and charging-equipment condition, user instructions and the condition of the electrical installation. NIPV identifies damaged cables and charging stations, battery-management faults, collisions with charging equipment and unnoticed defective packs as additional causes. Those conditions must be considered in the building's risk assessment.

Clear identification of electric vehicles and charging locations supports response. The source recommends recognisable charging spaces and information at entrances, while warning that clustering can increase travelling-fire exposure. Identification and spacing must therefore be assessed together.

Early detection supports suppression and evacuation. NIPV describes smoke, heat and carbon-monoxide detection options and stresses prompt alarm follow-up. It also notes that local standardisation and certification may not treat carbon-monoxide detection as a standard fire-detection method.

User instructions should address fault messages, distance from released gases, stopping charging, alerting the fire service and providing vehicle information. Public and private car parks require different communication arrangements. Instructions must match the people who actually use the space.

Runoff and residue require management. NIPV distinguishes cooling water in an immersion tank, which may be contaminated and must not go directly into the sewer, from other research on ordinary extinguishing water. The disposal route must be established for the actual water and residue.

Assessment and evidence limits

Battery fires require scenario-specific assessment rather than a single fire curve. Cell type, state of charge, pack design, external heat, ventilation and fire-service access can all alter the event. Evidence from one pack or vehicle should be compared carefully with the system being evaluated.

The likelihood of battery failure is itself uncertain. NIPV reports differing estimates and warns that technologies are still developing. It does not support a general claim that electric vehicles always have a higher or lower fire probability than conventional vehicles.

Suppression evidence is also incomplete. The report calls for research into which fixed systems best control incipient electric-vehicle fires and how travelling fires differ between vehicle types. A suppression measure that limits spread cannot be assumed to stop the pack's reactions.

Toxicity and environmental assessments must distinguish air, deposition, residue and contaminated water. Each can contain hazardous products, and a neutral surface pH reading does not prove the residue is free of hazardous substances. The complete exposure and disposal path matters.

The incident record should preserve those uncertainties alongside the chosen response. It should identify the pack, fire origin, gas and smoke pathways, cooling method, monitoring period and disposal arrangements. That gives a more accurate basis for judging both immediate and later consequences. It also shows which conclusions depend on a particular pack, test or operational assumption and therefore require renewed assessment when those conditions change.

See also

• Battery energy storage system
• Electric vehicle fire
• Thermal runaway

References

• U.S. Nuclear Regulatory Commission. (2005). Fire dynamics tools: Quantitative fire hazard analysis methods for the U.S. nuclear regulatory commission fire protection inspection program (NUREG-1805). Author.
• Van der Graaf, J., Hessels, T., & Rosmuller, N. (2021). Fire safety of indoor car parks accommodating electrically powered vehicles. Netherlands Institute for Public Safety (NIPV). English translation published 2023.