Can a car in flames really explode?

Agen is the scene of car fire episodes, temporarily leaving the sidewalks blackened by the vehicles who left smoke … but not shatter. Indeed, despite the impressive flames which escape from their habitacles at the time of the facts, no explosion has occurred during these events. And for good reason, contrary to what we could make us fear the scenarios of action films, the explosion of a vehicle when it is in the grip of flames, is a rare phenomenon these days. Without forgetting that in the cinema, the images of a spectacular fire ball, projecting the carcass of the vehicle in the air, do not represent reality …

Specific materials to avoid explosion

“A tire, under the effect of heat, will increase in volume, to give in. The windows, subjected to a thermal flow, can break. The airbags can be triggered,” details a soldier from the fire. This is how a car takes fire, important detonations can be heard.

And for good reason, current tanks, due to their design, are not so easily subject to an explosion. Whether it operates with petrol or diesel, a tank, made in a resistant material such as steel, metal or even a technical plastic, is thus made to face heat and shocks. Inside a vehicle, these are strategically placed remotely from the other elements that can generate significant heat.

If a vehicle with a plastic tank burns, “it pierces, it lets the fuel spread under the vehicle, which will feed the fire, but will not cause an explosion,” continues the firefighter.

Very rare explosion

“When a container, such as a bottle that contains liquid gas, is subjected to a high temperature, the internal pressure increases, the envelope breaks. It is then the vapors of this liquid that create the explosion. This is a phenomenon called the Bleve: Boiling Liquid Expanding Vapor Explusion”, he image.

However, in the case of car fire, only vapors emanating from liquid fuel can cause an explosion, only if these are mixed with air, in precise proportions. Although fuel emanations are much more flammable than that of diesel, in both cases, the explosion is a rare scenario, especially when the vehicle is in the open air, where the scents dissipate quickly.

Thus, the explosion of a vehicle can only intervene in very specific circumstances: when the fire reaches an almost empty tank filled with petrol vapors, or if materials that can cause the incident, such as pressure gas cylinders, are present in the vehicle.