Fighting fire with fire: Explosions used to snuff blazes


Researchers are working on fighting out-of-control bush fires with explosives, likening the process of using the sound wave produced by a blast to blowing out a candle.

Graham Doig of Sydney’s University of New South Wales has been examining how blasts can extinguish fires, a technique sometimes used on oil well blazes.

In one test, Doig detonated an explosion inside a 4-meter steel tube to produce a shock wave and rush of air aimed at a meter-high flame fueled by a propane burner.

“The sudden change in pressure across the shock wave, and then the impulse of the airflow behind it, pushed the flame straight off the fuel source,” he said. “As soon as the flame doesn’t have access to fuel anymore, it stops burning.”

Doig, from the university’s School of Mechanical and Manufacturing Engineering, said compressed air could also produce a blast wave, but would be harder to produce.

“The problem is you need a lot of compressed air,” he said.

“The beauty of explosives is, even though it sounds a lot more dangerous, you really only need a very small amount, and these kinds of explosives — nitroglycerin-style explosives — don’t spontaneously combust; you need a detonation charge to be applied to them.”

Doig said he hopes the concept can eventually be used to fight out-of-control fires in Australia and around the world, potentially by helicopters dropping explosives into fires.

“It’s not probably a case of ‘bang,’ fire extinguished, everybody goes home, it is one of many tools that will have to be applied to control a fire,” he said.

In the case of raging bush fires, which plague Australia during the summer months, the technique could perhaps be deployed to buy time, to get people out of the area.

He said the research is at the stage where he is starting to look at working with firefighters to see in what scenarios they feel they do not have any ways to tackle certain fires and this could be an option.

“We’re not saying it’s a magic bullet for every situation, but it could certainly apply in some scenarios — the trick is to do that in a very safe and controlled manner,” Doig said.