What caused a semi-truck to explode in Wilmington? Fire officials are searching for answers

Los Angeles fire officials have launched an investigation to determine how a semi-truck fire turned into a catastrophic explosion in Wilmington that injured nine firefighters, with one still hospitalized Friday.

The truck that exploded Thursday was powered by two 100-gallon cylinders of compressed natural gas that were mounted on either side of the vehicle. Compressed natural gas vehicles present different safety issues than gas-powered cars, particularly for responding firefighters.

It is not clear whether firefighters on the scene were aware before the explosion that the vehicle engulfed in flames was powered by compressed natural gas Vehicles equipped with natural gas fuel systems frequently have a diamond-shaped decal meant to identify how they’re powered. But it’s unknown whether the truck had a sticker or if it was visible when crews arrived.

Nicholas Prange, a spokesperson for the Fire Department, said the type of vehicle was not detailed in notes provided to the responding engine. It wasn’t until after the explosion that the notes were updated to reflect that it was a compressed natural gas truck.

“I’m not sure at what point that information became obvious to them,” Prange said. “No matter what we’re going to — a car fire, structure fire — we’re trained to observe, take in the big picture, and look for any clues as to what we’re going into.”

But certain details “might not be as obvious when there’s flames all around,” Prange said.

Fueling a vehicle with compressed natural gas presents unique safety issues because natural gas is stored at very high pressure — more than 3,000 pounds per square inch. The tanks are equipped with pressure relief devices that will open to let the gas vent safely when they reach a certain temperature, typically about 218 degrees.

Among other things, officials are trying to determine what caused the truck to catch fire. The driver, who was unharmed, told officials she noticed “abnormalities” in the two tanks that powered the vehicle, so she stepped outside and called 911.

Larry Stone, a former firefighter and safety director for waste companies who has trained fire departments on compressed natural gas vehicle safety, said that during Thursday’s fire it’s probably either “the pressure relief device failed to work or the firefighters were cooling the very device that would have prevented the explosion.”

The situation began with 10 firefighters responding to a report of a vehicle fire in the 1100 block of North Alameda Street shortly before 7 a.m. Thursday. The semi-truck, which did not have a trailer attached, was burning when they arrived. They applied water and had nearly extinguished the fire, according to the department, when the situation took a catastrophic turn.

Just six minutes after they stepped onto the scene, a compressed natural gas tank that helped power the truck exploded, according to the Fire Department.

The detonated cylinder was found hundreds of feet away after the explosion. The other cylinder shot flames for hours, and crews deployed a firefighting robot to douse the fire with water, according to the department.

Hexagon Agility, an Orange County-based company that manufactures natural gas fuel systems, wrote in a 2020 guide for first responders that crews should not apply water to the cylinders directly because it can prevent them from activating and result in an explosion.

The blast sent a plume of black smoke and flames 30 feet into the air, high enough to reach a transformer on a power line. The explosion threw some of the firefighters dozens of feet, knocking them out temporarily. The crew members who had more minor injuries rushed to help the more badly hurt, fire officials said.

A 37-year-old firefighter who has been with the Los Angeles Fire Department for nine years was being treated at the Los Angeles General Medical Center in the burn center intensive care unit.

Further details about the condition of the severely injured firefighter were not provided; on Sunday, however, Fire Department spokesperson Capt. Erik Scott said he had been removed from a ventilator. None of the injured firefighters have been identified by the department. In general, the nine firefighters suffered injuries that included burns, blunt trauma, shrapnel-inflicted wounds and hearing issues, Scott said.

“These firefighters that were injured are the brave people that respond when there’s an emergency, like when your vehicle is on fire,” he said. “Unfortunately, there’s inherent risks with our chosen profession that can have serious consequences.”

All the wounded firefighters remain off duty and “will receive ongoing treatment and support to begin this long healing process,” Scott said.

California

Nine L.A. firefighters injured, two critically, in semi-truck explosion in Wilmington

Several Los Angeles firefighters were injured in an explosion while they were trying to put out a truck fire, authorities said.

Feb. 15, 2024

Compressed natural gas vehicles have become more common in the last several decades, particularly in heavy-duty trucks and fleets — for example, trash trucks or public buses. Experts say these vehicles are no more or less safe than gasoline-powered vehicles, but their fuel is less expensive than gas and they create fewer smog-related tailpipe emissions.

In 2015, the pressure valves on a compressed natural gas recycling truck that had caught fire in Virginia opened, releasing natural gas that ignited and shot flames onto a nearby home. Stone said that was normal for the system and is a reminder that fire crews should look out for things that could catch fire near the truck when the valves release.

There have been a few reported explosions of compressed natural gas vehicles, particularly involving trash trucks. In 2015, a trash truck in Indianapolis exploded, damaging businesses. A firefighter was hit in the head by debris but was not seriously injured, the Indianapolis Star reported. A year later, a compressed natural gas powered garbage truck exploded in New Jersey, blasting a hole in a nearby house.

In 2019, a car powered by compressed natural gas was traveling through a bazaar in Bangladesh when the cylinder stored in the back of the vehicle exploded, the New York Times reported.

“It’s one of these things in the fire industry that happens on such a rare occasion that until it happens in your backyard it doesn’t get attention,” Stone said.

Researcher Scott Wilson contributed to this report.