Chemistry of Fire and Arson InvestigationBy Shelbi Sullivan

Summary

• Fire has been around for many years.• Thought of as one of the four

main elements before people even discovered the atom!• “The process in a fire is called

oxidation, where oxygen atoms combine with hydrogen and carbon to form water and carbon dioxide” (“How Does Fire Work?”). http://www.particleadventure.org/

images/page-elements/4-elements.jpg

Summary (continued)

• The fire triangle: fuel, oxygen, and heat (Groleau 1). • Arsonists use accelerants, substances

that easily catch on fire, to jumpstart a fire• Investigators usually can find out if a

fire was an accident or on purpose by using different clues about the fire (Rohrig 12-13).

http://upload.wikimedia.org/wikipedia/commons/thumb/2/20/Fire_triangle.svg/220px-Fire_triangle.svg.png

The Chemistry Behind Fire

• This oxidation reaction is usually called combustion because “the heat cannot be released faster than it is created” (“How Does Fire Work?”) • It has to have a fuel that will burn

enough to reach a certain temperature called kindling temperature (Rohrig 13)• The fuel can be a solid, liquid, or gas

(“Fire Behavior and Chemistry”).

The Chemistry (continued)

• This describes what happens when you light a match• When you scrape the match

over the surface, friction occurs which provides the heat to reach the kindling temperature. • Once the match is ignited,

the combustion leads to a chain reaction which sustains the fire (Groleau 1-2).

http://www.weirdlittleworlds.com/wp-uploads/2013/09/Fireplace_matches.jpg

Chemistry of Arson Investigation• Investigators use this knowledge to figure out if

fires started on accident from a faulty wire or if it was arson

• They first look at the patterns on the walls left by the fire

• Also, they use clues to pinpoint the origin of the fire

• The appearance of the wood after a fire can also be important (Rohrig 12-13).

http://www.tedfordpond.com/wp-content/uploads/Progressive_burn_composite2.jpg

Arson Investigation (continued)

• A major hint to whether it was arson or not is if there are traces of accelerant left• Some liquid accelerants that

weren’t completely burned can be left on the floor• These clues can lead

investigators to the origin of the fire(Rohrig 12-13).

http://www.csitechblog.com/.a/6a01348648f6e4970c0148c84393f6970c-pi

Implications

• Fire has been crucial to man for many years.• Provides us with heat and light and helps

us cook food• Fire is helpful but can also be dangerous if

we are not careful (“How Does Fire Work?”)• Knowing the chemistry of fire gives us the

knowledge of how to use fire to aid us and not hinder us

Works Cited

California Energy Commission, ed. "How Does Fire Work?" Energy Quest. Ed. Adam Gottlieb.

California Energy Commission, 22 Apr. 2002. Web. 28 Apr. 2014.

<http://www.energyquest.ca.gov/how_it_works/fire.html>.

"Fire Behavior and Chemistry." LBFD Training Center. Ed. Long Beach Fire Department. Long

Beach Fire Department Training Center, n.d. Web. 13 Apr. 2014.

<http://www.lbfdtraining.com/RTM/Chapter3%20Fundamentals/Fire%20Behavior%20&

%20Chemistry.html>.

Groleau, Rick. "On Fire: Strike a Match." NOVA Online. Ed. Public Broadcasting Services. PBS,

1 Jan. 2002. Web. 28 Apr. 2014.

<http://www.pbs.org/wgbh/nova/fireworks/fire_text.html>.

Rohrig, Brian. "The Chemistry of Arson Investigation." ChemMatters Apr. 2008: 12-14.

ChemMatters. Web. 13 Apr. 2014.