FIRE INVESTIGATION

CHEMISTRY OF FIRE

• Fire includes the combination of oxygen with other substances
• For a fire to be started, the ignition temperature must be reached
• The heat of combustion is the heat evolved when a substance burns

CHEMISTRY OF FIRE

• Another factor of fire is the rate or speed at which the oxidation takes place
• Flash point: a liquid burns when the temperature is high enough to vaporize it
• Pyrolysis: solid is hot enough to decompose into gaseous products
• Glowing combustion: burning at the fuel-air interface

CHEMISTRY OF FIRE

• Spontaneous combustion: result of a natural heat producing process in poorly ventilated containers or areas
• Use the following to initiate and sustain combustion: a fuel, oxygen and heat

SEARCHING THE FIRE SCENE

• Examine for signs of arson
• Most arsons started with petroleum-based accelerants
• Must focus on finding the fire's origin
• Fire has a tendency to move in an upward direction ; origin will most likely be the lowest point

COLLECTION/PRESERVATION OF ARSON EVIDENCE

• Ash, soot, and porous materials should be collected and stored in airtight containers
• Flammable liquid residues are able to be located with a vapor detector
• Control specimens should be collected
• Search for ignitors should be conducted

ANALYSIS OF FLAMMABLE RESIDUES

• Gas chromatograph is used for detecting and characterizing flammable residues
• It separates the hydrocarbon components and produces a pattern of a particular product
• Arsons initiated by petroleum distillates
• Comparisons of crime scene patterns to known flammable liquid patterns allows an analyst to identify the accelerant

PICTURE CITATIONS

• IRE . Photography. Encyclopædia Britannica ImageQuest. Web. 27 Mar 2015.
• Fire scene investigation. Photography. Encyclopædia Britannica ImageQuest. Web. 27 Mar 2015.
• Investigators from the Bureau of Alcohol, Tobacco, and Firearms, BATF, or ATF, examine the scene of a large fire that destroyed two multi-story buildings. They are investigating from a crane suspended basket and on the building itself.. Photograph. Encyclopædia Britannica ImageQuest. Web. 27 Mar 2015.
• Fire scene remains. Photography. Encyclopædia Britannica ImageQuest. Web. 27 Mar 2015.
• Photographing evidence. Photography. Encyclopædia Britannica ImageQuest. Web. 27 Mar 2015.