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Relationship between temperature and vapor pressure

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How Did The Fire Start?

How Did The Fire Start?


Credit: MSgt Christopher DeWitt
Source: http://commons.wikimedia.org/wiki/File:A_U.S._flag_hangs_in_front_of_a_burning_structure_in_Black_Forest,_Colo.,_June_12,_2013_130612-F-CD000-031.jpg
License: CC BY-NC 3.0

In 2012, arson caused some 267,000 fires in the U.S., resulting in 475 deaths, 2000 injuries, and approximately $1.4 billion in damages.  Detection of arson relies on a combination of good street detective work, careful study of the fire damage, and some very high-tech devices that can tell law enforcement officials exactly what started the fire and where it was started.

Why It Matters

  • Many reasons exist for why people start fires. One common reason is insurance fraud. If a building is lost because of a fire, the insurance company will pay at least some of the costs of replacement (even though the arsonist has no plans to rebuild). About half the arsons are committed by juveniles for many reasons: revenge, “sending a message”, vandalism. Other arsons result from the desire to cover up a crime (murder or fraud) or are the result of a mentally disturbed individual.
  • Credit: Ervins Stauhmanis
    Source: http://www.flickr.com/photos/ervins_strauhmanis/9554405492/
    License: CC BY-NC 3.0

    Unfortunately many forest fires are also started by arsonists, causing millions of dollars worth of damage each year [Figure2]

  • Obviously, not all suspicious fires are due to arson. Small children playing with matches, faulty electrical wiring, a stove left on – there are many natural causes for fires. Motive and circumstances can often easily be assessed with some interviews. Locating the start of the fire will often shed light on the cause.
  • Detecting arson is a long, arduous task that requires a lot of tools and personnel. Unlike television episodes, proving arson takes much longer than the average 45 minute (plus commercials) TV show. Burn patterns need to be studied, electrical wiring must be checked, the materials in the building need to be analyzed – all these tests often take weeks to complete.
  • One standard approach is to analyze for accelerants, the materials used to start the fire. These chemicals can be easily detected using sophisticated analytical techniques that rely on the boiling point of the material.
  • Arsonists are not always the brightest bulbs in the circuit.  One 17-year-old was attempting to siphon gas from a parked car to be used in starting a fire. Unfortunately for him, a detective was sitting in the front seat and quickly arrested the young man.
  • Watch a video on arson research: 


Explore More

With the links below, learn more about arson detection. Then answer the following questions.

  1. What are common accelerants used in arson?
  2. What is one quick way to detect accelerants at a fire?
  3. How does a gas chromatograph work?
  4. Where is the most likely place to find evidence of accelerants?

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