Fire in the Hopper of a Natural Gas Refuse Truck, North Texas (2022)

A waste hauler asked us in 2022 to investigate a fire on one of its compressed natural gas refuse trucks in North Texas. A consultant for another party attended our examination. Neither the hauler nor that party is identified here.

Smoke in the mirror

The truck had been working its route for several hours when the driver saw smoke from the hopper in the mirror. The driver tried a hand extinguisher, and the local fire department put the fire out with foam.

What the truck showed

The heaviest damage was on the left side behind the cab, in the engine compartment and in the cab itself. The left front tire had burned away and left a V pattern on the side of the hopper, and fire from that tire had moved into the cab. On the right side, a square burn pattern on the outside of the hopper wall had been made by heat from inside, and the tires on that side were intact and inflated. The inside of the hopper was rusted from the fire. The battery in its left side compartment was badly damaged but intact, and the natural gas tanks on top of the hopper had no damage.

Ruling things out

The wiring was heavily heat damaged, but we found no arc point on any conductor, so the electrical system was ruled out as an ignition source in the area of origin. We found no mechanical failure there either. The compactor blade was in its forward position, with the load packed toward the rear of the hopper.

A fire that rode in with the load

The area of origin was inside the hopper. The exact point of origin and the first fuel could not be fixed, but the most likely first fuel was the garbage itself, ignited by a source inside the load that could not be identified. Fleet operators send us fires like this one for vehicle fire investigation.