Hot spotter: life of a fire investigator

By Kathy Riley 1 July 2009
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Where there’s smoke, there’s a fire investigator.

It was the kind of blaze that NSW fire investigator Tony Cafe calls a gorilla: big, mean and nasty. The hardware store in southern Sydney was the size of a football field, and it had been burning for three days. When Tony was given the go-ahead, excavators were still knocking down walls and turning over smouldering piles of rubble for firefighters to hose down. A choking, acrid smell clogged the air, and everything was wet. “You need to watch the runoff,” Tony says. “It could be toxic.”

Armed with a shovel and a camera, “an investigator’s two best friends”, Tony began combing the scene looking for burn patterns. “Fires initially burn upward in a V shape, so if the blaze began near a wall, this is the pattern it will leave,” he says. “If the fire began in the centre of a room, there’ll be a pattern on the ceiling. If the fire was too severe and all the walls are burnt, you have to rely on other things, such as the remains of electrical wiring.”

Sometimes the clues to a fire are easy to find: a blackened toaster, a tree split by lightning, the heady scent of petrol. Often they’re not, which is why fire investigation has a reputation as one of the toughest of the forensic sciences. Only those with an intimate understanding of fire and fire behaviour need apply.

Before inspecting the scene itself, fire investigators interview witnesses, neighbours and firefighters, and gather information about weather conditions. Every blaze is treated as a crime scene until proven otherwise. If the fire is deemed suspicious, police are called in to deal with issues of liability and responsibility.

In the bush, investigators observe grass stems; ash deposits; burn patterns on trees, stumps, rocks and posts; and a phenomenon known as “leaf freeze”, where fire-dried leaves remain rigidly pointing in the direction the fire has travelled. “We work backward against the direction of the fire until we reach the point of origin, which can often be narrowed down to 4 or even 1 sq. m,” says Gerard Seppelt of the Country Fire Service, SA. Accelerants such as petrol leave a trail, too. When water drains from the scene, the accelerant begins to evaporate, creating a plume that can be detected for days after the fire by trained sniffer dogs.

It took a few days at the hardware store, but eventually Tony found the culprit. The connector in one of the store’s neon signs revealed tracking damage, where moisture or another substance had created a current leak across the surface of the connector. This in turn formed a carbonised – and flammable – track. No arson, no-one hurt, no case for a lawsuit. For such an enormous fire, it’s a blessedly benign conclusion.

Although rural and urban fire investigators require different training and rarely cross professional paths, they agree that finding the cause is only half of their mandate. The other half is trying to get ahead of future trends in fire ignition to save more lives, houses and bushland. Says leading Victorian rural fire investigator and trainer Fabian Crowe: “I’ve seen a dramatic decrease in the number of escaped fires from farmers’ burns in Victoria over the past 10 years, which I put down to the fact that investigators have been able to educate them on why it escaped. This is all about improving ways to prevent, contain and fight fire in the future.”

Australian Geographic Jul – Sep 2008