When firefighters arrived on scene, they asked the driver to dump his load in the street, which would reduce the risk of anything on the truck itself—gasoline, CNG, etc.—catching fire. Then the firefighters could put out the blaze easily, treating it like a normal trash fire, and have Groot haul away the debris afterward. But this didn’t work either. The flames had spread far enough by this point to put the truck’s dumping mechanism out of commission.
So, firefighters unrolled hoses and hooked up to a nearby fire hydrant. They recognized that the truck was CNG-powered, as were many Groot vehicles. CNG offers a lower maintenance cost, uses less fuel, and creates less pollution than diesel, but best practices currently suggest not spraying CNG cylinders directly with water. Firefighters instead tried to aim water right into the back of the garbage truck without wetting the CNG cylinders nearby on the roof.
They were waiting for the telltale hiss of the pressure relief system to trigger. These valves typically open within two to five minutes, depending on fire conditions, and they should be capable of venting all their natural gas some minutes before the CNG canisters would otherwise be in danger of exploding. But the hiss never came, and as Fire Chief Lance Harris and his crew worked to secure the scene and put water onto the burning load, the CNG canisters exploded catastrophically instead.
The explosion, as captured by a bodycam.
In a board of trustees meeting this week in Arlington Heights, Harris recounted the incident, noting that he felt lucky to be alive—and thankful that no township personnel or residents sustained serious injuries.
“We can’t prove it,” he said, but after two months of investigating the situation, his department had concluded with high probability that the fire had been caused by a lithium-ion battery discarded into a recycling container. This suspicion was based on the amount of fire and the heat and speed with which it burned; lithium-ion batteries that enter “thermal runaway” can burn hot, at around 750° Fahrenheit (399° C).
Harris’ takeaway was clear: recycle even small lithium-ion batteries responsibly, as they can cause real hazards if placed into the waste system, where they are often impacted or compressed.
