What Is Thermal Runaway? EV Battery Fires Explained

Thermal runaway explained: why battery fires are different

The single most important concept in battery fire safety has a name: thermal runaway. Understanding it explains almost everything about why these fires behave the way they do.

A lithium-ion battery stores a large amount of energy in a small, sealed space. When a single cell is damaged, overheated or internally short-circuited, it can begin to heat itself uncontrollably. UL Research Institute defines thermal runaway as a cell entering a self-heating state it cannot recover from (Task Force Tips, 2025).

A chain reaction inside the pack

The heat from one failing cell raises the temperature of its neighbours until they fail too — a cascading reaction often compared to a row of touching matchsticks (CBS News, 2023). As cells break down, they vent toxic and flammable gases including hydrogen fluoride and carbon monoxide, and the fire can reach temperatures beyond 1,000°C (EV Fire Protection, 2025).

Crucially, compromised cells release their own oxygen as they decompose, which means the fire is partly self-feeding. That is why simply smothering the flames is rarely enough — the reaction continues inside the pack even when visible flames are gone (International Council on Clean Transportation, 2024).

Why containment matters

Because thermal runaway is so hard to stop once it starts, the smartest strategy is to contain the event and limit how far it can spread. A high-temperature EV fire blanket is designed to do exactly that — wrapping or covering the device to isolate it and protect surroundings while heat dissipates. For larger or repeated risks, a heavy-duty high-silica blanket withstands the extreme temperatures these fires generate.