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LITTLETON, Colo. -- A towering spray of gasoline and then an eruption of flames – that’s what happened during a demonstration created for Contact7 to warn of a potential danger that many people may have sitting in their garage or driveway.
"If it geysers and that gasoline gets ignited you can have property damage, serious injuries, you can even have deaths," said Dennis Shelp, a forensic engineer at Advanced Engineering Investigations.
Part of his job often involves re-creating life and death scenarios, and he said gas geysering is one of them.
"This can happen, yes, and has happened," Shelp said.
A team of engineers monitored a black gas tank, which sat in a heated water bath and simulates the radiant heating an external gas tank would receive during outdoor use.
"When you have a hot gas tank that doesn't vent properly, we could see the tank bulging as the vapors built up inside," Shelp said.
With the Littleton Fire Department standing by, the experiment got underway. One engineer in protective clothing used a pull-line to take the cap off quickly from several yards away.
Gas shot up more than 15 feet in the air before catching fire.
"If the operator is right there taking off the cap, there is serious potential for burns – even death," said Shelp.
He said it can happen with gas-powered equipment like chainsaws, lawnmowers and ATVs – all tools used outdoors, where gas cap vents can easily become blocked by dirt, soot or mud.
"It's not just the pressure. It's also the fact the gasoline is above its boiling temperature," said Shelp. “When you release the pressure, it rapidly boils and erupts and sprays out.”
The heating can come from a combination of factors, including the sun, the atmosphere and the engine itself.
And it’s not just hot gasoline that can cause severe injuries.
"In a real-world scenario, one possible ignition source would be hot exhaust, surfaces of hot exhaust, the muffler," said Shelp. "There also could be a static discharge."
A video by the USDA Forest Service features a Colorado firefighter who experienced gas geysering. Nic Hoisington was part of a hotshot crew managing a controlled burn in Larimer County.
He was standing in ash on a fire line, but there were tiny pockets of open flame nearby.
When his chainsaw would not start, he thought it was out of gas.
"Pop the cap just to see what was in there, and at that point is where it geysered on me," Hoisington said, "I caught fire...the whole right side of my body went up in flames."
Schlep said people often miss the warning signs of geysering, like an engine that is running rough or backfiring, a hissing sound coming from the tanks, the tank bulging or a strong odor of gasoline.
He said if you notice any of these, never take off the gas cap.
"Allow the engine to cool. Allow the gas tank to cool. Note that the bulging has gone down and you don't hear hissing anymore before you attempt to open the gas tank," Shelp said.
He said the biggest risk of geysering is on older equipment built before 2011.
However, Contact7 found recalls for ATV models from as recently as 2013, 2014 and 2015 for fire and burn hazards caused by gas caps and tanks that do not vent properly.
Venting on most newer gas tanks and gas caps has been updated to prevent clogging.
For older equipment, cleaning it and checking for clogs can lower the risk of gas geysering.
Using the right gas cap is important because a diesel cap will not vent properly for a gas-powered engine. To check to see if a piece of equipment is under recall, click here.