FIRE INVESTIGATION

THE CHEMISTRY OF FIRE

• fire is a type of oxidation; the combination of oxygen + other substances to make new substance
• ignition temperature must be reached in order for a fire to start
• Rate + speed in fire investigation must also be determined
• Liquid burns when flash point is reached
• Spontaneous combustion, rare, is the result of natural heat producing in poorly ventilated areas

SEARCHING THE FIRE SCENE

• the arson investigator begins to examine scene of fire for signs of accelerant when fire is extinguished
• petroleum-based accelerants are most common in arson cases
• Origin of fire must be determined
• signs of arson include signs of separate fires, the use of “streamers” to spread the fire, and burns found on floor as opposed to the ceiling of a structure, due to an accelerant.

COLLECTION AND PRESERVATION OF ARSON EVIDENCE

• evidence like ash, soot, porous materials, etc. should be collected and placed in airtight containers
• A vapor detector can detect traces of an accelerant
• Control specimens should also be collected as reference samples
• Ignitors such as matches should be looked for
• Parts of a Molotov cocktail (bottle-based improvised incendiary weapon) should also be looked for

ANALYSIS OF FLAMMABLE RESIDUES

• Most arsons are initiated by petroleum starters like gasoline
• the gas chromatograph is the best took for detecting flammable residues.
• It does this by separating hydrocarbons to produce a pattern that can match petroleum products
• By comparing petroleum recipes with samples from the scene of an arson fire, investigators can match it to a specific product

PHOTOS CITED

• FIRE . Photography. Encyclopædia Britannica ImageQuest. Web. 27 Mar 2015.
• Fire. Photograph. Encyclopædia Britannica ImageQuest. Web. 27 Mar 2015.
• FIRE . Photography. Encyclopædia Britannica ImageQuest. Web. 27 Mar 2015.
• FIRE. Photography. Encyclopædia Britannica ImageQuest. Web. 27 Mar 2015.