How Do Experts Investigate Fires?
DENVER (CBS4) – As the weather gets colder, the fires seem to get bigger. There’s no doubt there’s an increase in fires caused by faulty heaters. But what about the fires that are human caused? One might think there’s been an increase in arson. But Denver fire investigator Kathleen Vredenburgh is not seeing it in homes and buildings — in spite of the bad economy.
Cars — well that’s another matter.
“We’ve had a rise in car fires and I think there’s probably a direct relationship between that and our economic situation where people are buying cars they can’t afford and they choose to burn them in order to collect the insurance money and not be held to the car payment anymore.”
The problem for arsonists is often that too many people know. Fire science may be more sophisticated than years ago, but it’s often the interviews Vredenburgh and her colleagues do that breaks cases.
“It’s really hard to hide your history and the people around you who know you and those are all people we talk to. And I think that people have this false notion that, ‘If I burn it, that will get rid of all the evidence.’ And that just doesn’t really happen that way.”
Because in modern fire investigation, they use new techniques to reveal dogs to sniff out accelerants and now even mechanical devices that can detect the accelerants.
“Actually fire science has changed a lot,” Vredenburgh said. “A lot of the things that we believed as fact as it related to accelerants and the ways that fire started and the patterns that they make have changed.”
But a lot of the basics of fire investigation remain true.
“A lot of times you smell it,” Vredenburgh said. “Sometimes you will find what we call trailers, which is when you will find a line from where we believe the fire started and going away where there’s no fire at all.”
To get started, you have to find what appears to be the area where the fire started. Investigators can sometimes narrow it down to the exact spot. Then they eliminate what may have ignited it.
“You look at what are all my possible sources of ignition, or ways that the fire may have started. You check the electrical, you look to see if they are burning candles, if they were burning incense and you look to see what the witness statements are, what were they doing in that corner.”
Different materials leave different burn patterns. Modern construction is so saturated with plastic; that can influence fire behavior and investigation. And there are differences in the concentration of heat.
“People think that if you burn something with gasoline, that it burns really hot and really fast. But the truth of it is that the heat release rate with wood is actually higher with wood than it is with gasoline.”
Of course there’s little similarity to the investigators you see pictured on one hour long TV shows. Vredenburgh points out that she’s often waiting a while for lab results. But there is one aspect of fire investigation that may be more like television dramas than other forms of investigation. They are often working a case start to finish. It might take a long time and arrests may be rare, but it’s worth it when their work comes through.