FIRE INVESTIGATION

1. CHEMISTRY OF FIRE

• Fire is technically defined as a type of oxidation.
• Ignition temperature, which is the minimum temperature to ignite fuel, needs to be reached.
• Heat of combustion is the heat evolved when a substance burns.

CHEM. OF FIRE CONT.

• Fire can be explained with the rate of speed in which oxidation takes place.
• Fuel will only produce a flame when in a gaseous state.
• The flash point is when the temperature is high enough to vaporize a liquid.
• Pyrolysis is when a solid is hot enough to become a gas.

CHEM. OF FIRE CONT.

• When object, such as a cigarette, is burning at the fuel-air interface it is called glowing combustion or smoldering.
• The result of a natural heat-producing process in poorly ventilated containers or areas is a rare occurrence called spontaneous combustion.
• To initiate combustion there must be a fuel, sufficient oxygen, and applied heat.

2. SEARCHING THE FIRE SCENE

• As soon as the fire is extinguished, the investigation begins.
• Immediate investigation takes precedence over the obtainment of a search warrant.
• The main focus is the investigation is finding the fire's origin.

SEARCHING THE FORE SCENE CONT.

• Signs of arson include evidence of separate and unconnected fires, the use of “streamers” to spread the fire from one area to another, and evidence of severe burning found on the floor as opposed to the ceiling of a structure, due to a flammable liquid.
• In a fire, combustible liquids are rarely entirely consumed, this leaving r eminence and residues.

3. COLLECTION/PRESERVATION OF ARSON EVIDENCE

• Ash and soot, along with porous materials which may contain excess accelerant, should be collected and stored in airtight containers, leaving an airspace to remove samples.
• A vapor detector helps find traces of flammable liquid residues.
• Uncontaminated control specimens must be collected.
• Igniters must also be collected.

4. ANALYSIS OF FLAMMABLE RESIDUES

• In the laboratory, the gas chromatograph is the most sensitive and reliable instrument for detecting and characterizing flammable residues.
• The majority of arson crimes are initiated by petroleum distillates such as gasoline and kerosene.
• The gas chromatograph separates the hydrocarbon components and produces a chromatographic pattern characteristic of a particular petroleum product.
• By comparing select gas chromatographic peaks recovered from fire-scene debris to known flammable liquids, a forensic analyst may be able to identify the accelerant used to initiate the fire.

WORKS CITED

• Suspect Arrested In Slew Of Los Angeles Arson Fires. Photography. Encyclopedia Britannica ImageQuest. Web. 27 Mar 2015.
• Burning coal. Photograph. Encyclopedia Britannica ImageQuest. Web. 27 Mar 2015.
• Burning match. Photograph. Encyclopedia Britannica ImageQuest. Web. 27 Mar 2015.
• Flames. Photograph. I Britannica ImageQuest. Web. 27 Mar 2015.
• Burning house. Photography. Encyclopedia Britannica ImageQuest. Web. 27 Mar 2015.
• Flaming fire lighter. Photograph. Encyclopedia Britannica ImageQuest. Web. 27 Mar 2015.
• Flames during fire test of tunnel lining. Photograph. Encyclopedia Britannica ImageQuest. Web. 27 Mar 2015.
• Fire. Photograph. Encyclopedia Britannica ImageQuest. Web. 27 Mar 2015.