FIRE INVESTIGATION

CHEMISTRY OF FIRE

• Fire is a type of oxidation
• Combination of oxygen and other chemicals
• Ignition temperature must be reached in order to ignite fuel
• The heat from a burning substance is called heat of combustion

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• A fuel will react with oxygen only in a gaseous state
• Liquid burns when a temperature if high enough to vaporize it(flashpoint)
• Solids but be hit enough to decompose into gas (pyrolysis)
• Spontaneous combustion -heat producing in poorly ventilated area

COMBUSTION

• A fuel must be present
• Oxygen must combine with the fuel
• Heat is needed to initiate combustion
• Heat also sustains the reaction

SEARCHING FOR THE FIRE SCENE

• Once fire is extinguished, investigators must search for signs of arson
• Most arsonist start with an accelerant
• Must find the fires origin
• Other signs: separate fires,"streamers", and severe burning on floor and ceiling
• Combustible liquids rarely get fully burned by fire

COLLECTION OF ARSON EVIDENCE

• Ashes and materials containing accelerant should be collected
• Evidence collected should be in air tight containers
• Vapor detector helps locate traces of flammable liquids
• Ignitors must be found and collected

ANALYSIS OF FLAMMABLE RESIDUES

• Gas chromatography is used to detecting flammable residues
• Most reliable
• Also characterizes the flammable residues
• Separates the hydrocarbon components
• Produces a chromatographic pattern

IM DONE

CITATION

• An Under-construction Building Ablaze In Nanning. Photography. Encyclopædia Britannica ImageQuest. Web. 25 Mar 2015.
• Car in flames. Photography. Encyclopædia Britannica ImageQuest. Web. 25 Mar 2015.
• Fire In Office Tower Under Construction In Beijing's CBD. Photographer. Encyclopædia Britannica ImageQuest. Web. 25 Mar 2015.
• Residents Return To Mobile Home Park Devastated By So Cal Fires. Photographer. Encyclopædia Britannica ImageQuest. Web. 25 Mar 2015.
• Firefighters examining evidence. Photography. Encyclopædia Britannica ImageQuest. Web. 25 Mar 2015.
• Fire fighters hosing a fire at a piano factory. Photography. Encyclopædia Britannica ImageQuest. Web. 25 Mar 2015.
• Fire Fighter Spraying Huge Fire. Photograph. Encyclopædia Britannica ImageQuest. Web. 25 Mar 2015.