The Chemistry of Fire and Arson Investigation

1. By Shelbi Sullivan

2. • 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/p
age-elements/4-elements.jpg

3. 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/t
humb/2/20/Fire_triangle.svg/220px-
Fire_triangle.svg.png
Summary (continued)

4. • 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”).

5. 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_matche
s.jpg
The Chemistry (continued)

6. • 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

7. • 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/6a01348648f6e4970c0148c84393f6
970c-pi

8. • 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

9. 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.