Arson & Explosions

Arson & Explosions - Arson& Explosion Investigations...

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Unformatted text preview: Arson & Explosion Investigations Investigation r Difficult scenes to investigate  Evidence is largely destroyed by the explosion or fire  Efforts to extinguish fire also destroy evidence  Forensic Scientist’s duty: to detect and identify igniters, accelerants and detonating materials present (indicating arson), or determine that there are none (indicating accidental causes) Accidental Fires r Faulty wiring  Defective appliance  Untended fireplace  Candles left burning  Falling asleep while smoking  Stovetops burners left on  Knocking over burning grills or candles  Kitchen flare ups  Irons left on (including curling irons)  Lightning Important Definitions • Oxidation : the combination of oxygen with another substance to produce new substances  Energy : the combined ability or potential of a system or material to do work  heat, light, nuclear, electrical, mechanical, chemical  Combustion : rapid combination of oxygen with another substance accompanied by heat & light  Simply, fire requires heat, fuel & air (oxygen) Chemistry of Fire r Energy is required to begin a reaction  Fire requires heat energy  Substances have energy barriers which must be overcome by heat energy in order to start oxidation  The required heat energy is the ignition temperature of the fuel Chemistry of Fire r Fuel reacts with oxygen to produce flame only when the fuel is in a gaseous or vapor state… even if the fuel is a solid or liquid!  Temperature must be high enough to vaporize the fuel  Liquid Fuels  The flashpoint of a liquid fuel is the lowest temperature at which the liquid gives off sufficient vapor to support combustion  Solid Fuels  Solid must be hot enough to produce gaseous products  Chemical breakdown of solids to gas --> pyrolysis...
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This note was uploaded on 09/08/2010 for the course JS 112 at San Jose State.

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Arson & Explosions - Arson& Explosion Investigations...

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