The Fire
Arson investigation starts with the fire itself. To create and sustain a fire three factors must be present. The three factors are known as the fire triangle (Peige ed., 1977). The fire triangle consists of oxygen, a fuel source, and heat. In most cases the percentage of oxygen concentration must be above 16% (Peige, ed., 1977). The fuel may be any flammable substance. The heat source needs only to match the ignition temperature of the fuel.
In a fire involving arson the arsonist will have tampered with one or more of the factors in the fire triangle. The arsonist may increase the fuel load by introducing flammable material or by adding accelerants such as kerosene, gasoline or alcohol (French, 1979) The arsonist may increase the oxygen content of a structure by opening windows or punching holes in ceilings and walls (French, 1979) Fire will follow the highest concentration of oxygen to its source. By ventilating a structure at the top and starting a fire at the bottom of the structure an arsonist can cause the fire to race upward through the structure. The fire will rapidly involve the whole structure rather than be confined to one room.
