CSI And Arson
How does a fire ignite?
A fire ignites when a fuel comes into contact with a heated source that is hot enough to vaporize the fuel and if you have oxygen in the area. You then have a vapor fuel. You then have oxygen and you then have a heat source and those are the three important ingredients of fire. You'll have fire. You need heat, you need fuel in a vapor state and you need oxygen.
How does learning where the fire originated help in CSI?
The first thing that the forensic scientist has to ascertain is whether there is the possibility of arson. That is, whether a perpetrator added an accelerant to start the fire. Where the fire began, and how the flames travelled through the structure, will help answer the question as to whether there is the possibility that an accelerant existed. If that possibility is likely, then samplings will be taken of material collected at the scene of the fire and they will be analyzed for the presence of an accelerant at the crime lab.
How does a fire grow?
Fire is a chain reaction. As materials burn, they vaporize fuel and the fuel comes in contact with oxygen or air. One other thing that is happening is that as the oxygen, when the oxygen is combining with the fuel, it is also creating heat, so it's a vicious chain reaction. As a fire burns, it creates more vapour fuel. The air is always present and it also creates heat energy and feeds itself. A fire is a vicious chain reaction.
How does learning the way a fire grew help in CSI?
Fire investigations obviously begins at the scene of the fire. It's important that the investigators locate the point of origin of the fire, because it's at that point where you will expect to find an accelerant, and that is what we are looking for in the forensic laboratory, something that contributed to the start of the fire, like gasoline, kerosene or some other hydrocarbon. What an arson investigator is trained to do is to look for the point of origin, which is the closest to lowest point that shows the most intense burning or charring at the scene of the fire, because it's at that point that you would expect to find the point of origin. And it's at that point that collections would be made and brought back to the laboratory where they will be looked at for the present of accelerants, kerosene, gasoline, etc.
What are 'fire accelerants' and how are they used to progress a fire?
How is evidence from a fire collected and preserved in CSI?
Well, that's pretty simple. As I said, we're really interested in forensic science and that includes looking for accelerants at crime scenes. So, when collections are made at crime scenes, you want to put those collections in an air tight container. We normally recommend air tight clean paint cans. They come in various sizes, and they're normally unbreakable, and well sealed. But a mason jar will do as well. But it's got to be put in an airtight container. You should not put those kind of materials in plastic bags. The plastic will interact with the accelerant, destroy it, and the accelerant will also vaporize right through the plastic as well. So do not use plastic containers when collecting fire debris.
