Vehicle fire

An SUV on fire in Pasadena, California

the owner watches as firefighters arrive on the scene of an SUV fire in 2005

A car fire, or auto fire, is one of the more common causes of fire-related property damage. There is roughly one motor-vehicle fire every 96 seconds in the USA.

In the UK, accidental car fires are declining but deliberate car fires (arson) are increasing. Most car fires are deliberate in the UK. It is common for joyriders to set fire to stolen cars: abandoned cars are commonly set on fire by vandals. Around two cars out every thousand registered in the UK catch fire each year.

Hazards

A motor vehicle contains many types flammable fuel, including flammable liquids like gasoline and oil as well as solid combustibles, including the car's upholstery and detonators in safety devices (e.g. airbags). Cars also house multiple potential sources of ignition, such as electrical short circuits or fuel leakages onto hot exhaust systems. Fuel leaks from fractured fuel lines will rapidly ignite and faulty lines have been known to cause numerous fires. Also, car batteries pose a fairly unique hazard in themselves: hydrogen gas evolved in the electrolysis reaction ignites readily in fire conditions and can result in an explosive dispersion of battery acid. Modern car safety devices can also pose unique hazards in fires: detonators used in air bag systems can explode, bumpers with specially designed "crush zones" can release sulfuric acid when heated, and the wiring in electric and hybrid cars can cause accidental electrocution. Electric and hybrid cars have large batteries, usually NiMH, lead-acid, or Li-ion. Besides the obvious hazard of electric shock, these batteries can create other hazards. Li-ion batteries can explode rapidly and in chain reaction. Lead-acid batteries can release hydrogen or melt and leak sulfuric acid. Ni-MH batteries can burn and leak chemicals as well, but their hazards are usually less severe. In most cases, a large battery is less dangerous than a gas tank. Most large batteries for electric cars or hybrids have built-in safety features to prevent the battery from starting a fire such as smoke detectors, temperature sensors, and overcharge protection.

It is often the case in non-arson auto fires that the bulk of the fire is (at least initially) contained in the engine compartment of the vehicle. In most vehicles, the passenger compartment is protected from engine compartment fire by a device called a firewall.

Recommended action

The recommended action in case of car fire is:

• If the vehicle is moving, politely signal and move to the shoulder or side of the road.
• Shut off the engine.
• Get yourself and all other occupants out of the vehicle.
• Get far away from the vehicle and stay away from it. Keep onlookers and others away.
• Warn oncoming traffic.
• Notify the fire department.
• Do not attempt to try to put out the fire yourself.

The last is important due to the risk of explosion and the toxic fumes emanating from vehicles fires. Inhalation of toxic fumes is the most common form of fire-related death.

Opening the hood (bonnet) of a car which may be on fire is especially dangerous, as it allows a rapid and significant surge of air into the engine compartment, which may cause a rapid increase in fire intensity. Some countries require the carrying of a fire extinguisher. This should not be seen as overriding the advice above. It has been suggested that, when using a fire extinguisher on an engine fire, the extinguisher should be fully discharged through the gap created by simply releasing (but not lifting) the hood, and then the car should be left until the fire crew have pronounced it safe. As with all fires, residual hot spots may cause the fire to flare up again when fresh oxygen is supplied.

Also see

• Forensic engineering