Vehicle Fire Hazards
Plastic Fuel Tanks
Firefighters are experiencing an increase in fuel spill fires involving flammable ethanol/gasoline mixtures. Since the late 1980s, more plastics have been u... View MoreVehicle Fire Hazards
Plastic Fuel Tanks
Firefighters are experiencing an increase in fuel spill fires involving flammable ethanol/gasoline mixtures. Since the late 1980s, more plastics have been used in place of pressed steel for fuel tanks. Up to 70% of all fuel tanks produced in North America are made of plastics. Although plastic fuel tanks will retard the rise in fuel temperature from a well-involved vehicle fire, they will soften, sag, and eventually release the fuel onto the ground, potentially creating a running fuel fire requiring the use of alcohol resistant (AR) foam. Alternatively, a dry chemical fire extinguisher may also be effective on such fires. Anticipate fuel tank failures at well-involved vehicle fires, and stage apparatus away from the potential path of flowing fuels.
Less common, but still dangerous, are fires involving vehicles powered by alternative fuels such as compressed natural gas (CNG), marked by a blue diamond badging. Although these vehicles make up only about 0.1% of the total vehicles on the road in the United States, CNG is becoming extremely common on refuse trucks and public transit buses (12-15%). Some light trucks and cars, such as the Honda Civic, the Chevrolet Silverado 2500, and the Ford F250, may also be CNG-powered. CNG conversion kits are available for many other passenger cars, trucks, and SUVs.
When a CNG vehicle is on fire, approach with extreme caution. Several well-documented cases of explosions involving CNG vehicles have occurred, including in Seattle, Washington (Honda Civic); Indianapolis, Indiana; and Hamilton, New Jersey (refuse trucks).
CNG vehicle fuel tanks are pressurized to 3,600 psi and are equipped with pressure-relief devices (PRDs). If responding to a CNG vehicle fire that does not involve the tanks, proceed with normal firefighting operations. However, if the CNG tanks are involved or the heat of the fire has raised the tank�s temperature and activated the PRD (generally resulting in a loud jet of fire emitting from the PRD), set up a safety perimeter of at least 100 feet around the vehicle, protect exposures, and let the vehicle burn. Either the tanks will rupture or the CNG will vent until the tanks are empty.
If fire is impinging on the CNG tanks and the PRD fails to operate, the pressure in the tanks will rapidly rise; the tanks will fail when the pressure reaches 8,000-9,000 psi. Even if the PRD is operating normally, a CNG cylinder will survive in a fire only for about 20 to 30 minutes. In a bystander video of a 2016 trash truck fire in Hamilton, New Jersey, you can clearly see and hear flames and gas venting from a PRD. Despite the fact that the PRD seems to be operating as designed, the cylinder suffers a catastrophic failure and explodes only seconds before firefighters arrive.
Steven Schnaudt
