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Arson Analysis of Fire

Arson is defined as purposely setting fire to a house, building or other property. Arson is the second leading cause of death by fire in the U.S. An estimated 500 Americans died in arson-related fires. Arson caused more than $2 billion in property damage.

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Arson Analysis of Fire

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  1. Arson is defined as purposely setting fire to a house, building or other property. Arson is the second leading cause of death by fire in the U.S. An estimated 500 Americans died in arson-related fires. Arson caused more than $2 billion in property damage. Only 19% of arson cases resulted in arrest, and only 2% were convicted. 50% of arsonists are under the age of 20 (40% are under 15 years old). ArsonAnalysis of Fire

  2. Arson Investigation • Ignition temperature. • Combustion will continue until: • Fuels are consumed. • Oxidizing agent has been removed. • Fuels are cooled below their ignition temperature. • Flames are chemically retarded. • Transfer of heat. : • Conduction. • Convection. • Radiation. • Direct flame contact.

  3. Ignition temperature and flash points are NOT related! Arson Investigation • Definitions. • Flammable liquid. • Combustible liquid. • Flammable. • Flammable or explosive limits. • Vapor density.

  4. Flash point - The temperature at which a particular flammable liquid gives off vapors (vaporizes) and therefore can ignite. The ignition temperature is the temperature required for a liquid to continue to emit vapors that can sustain combustion. A flammable liquid in its liquid state will not burn. It only will ignite when it vaporizes into a gaseous state. All flammable liquids give off vapors that can ignite and burn when an ignition source such as a lighted cigarette or spark is present.

  5. Interior Examination. • Work backward in relation to fire travel and from least to most damage. • In accidental fires, floor damage is limited in respect to the ceiling damage. • “V” patterns may help locate POO. Arson Investigation • Point of Origin (POO). • Defined as where the fire originated. • Cause of fire may be near the POO. • Fire usually burns longer at POO. • If accelerants or ignition devices used, they may be present at the POO. • Multiple POO’s MAY indicate arson. • “V” patterns usually point to the POO. • Extensive ceiling damages may be present above the POO. Point of Origin (POO).

  6. Arson Investigation

  7. Accelerants are any liquid, solid or gaseous material that will sustain or enhance flammability. Liquid materials are commonly used because of ease of ignition and familiarity of use. Accelerants are nearly exclusively derived from hydrocarbons. Straight chain hydrocarbons are the backbone of the oil industry. Hydrocarbons are molecules made up of the elements hydrogen and carbon. Octane is a term familiar to all. It consists of a hydrocarbon having 8 carbons. Examples: Gasoline Kerosene Diesel Lighter fluids Charcoal starters Automobile additives Camping fuels Accelerants

  8. Classification of Accelerants 1. Light petroleum distillates (LPD) 2. Gasoline 3. Medium petroleum distillates (MPD) 4. Kerosene 5. Heavy petroleum distillates (HPD) 6. Miscellaneous

  9. Evidence of Accelerants • Large amounts of damage • Unusual burn patterns • High heat stress • Multiple sites of origin • “Sniffers” • Portable gas chromatographs • Chemical tests • Canines • Portable detectors • Detect change in oxygen level on a semiconductor • Guides to the best place to collect samples Dogs can detect 0.01 mL of 50% evaporated gasoline 100% of the time. 0.01 mL is about the size of a thousandth of a drop.

  10. Evidence Containers Steps to Recover and Identify Accelerants • The evidence container should have the following qualities: • Air tight • Highly resistant to breakage • Prevents cross-contamination • Good integrity seal • Collect samples. • Extract the fire debris and obtain a sample for instrumental analysis. • Carry out instrumental analysis. • Interpret the results.

  11. Accelerant Identification : Extraction • Common methods used today: • Steam distillation • Vacuum distillation • Solvent extraction • Charcoal sampling • Swept headspace .

  12. Analysis A gas chromatograph is coupled to a mass selective detector. • The vial is automatically injected on the gas chromatograph / mass selective detector (GC/MSD). • The GC will separate all of the sample’s components. • The MSD will identify the sample’s components.

  13. No Ignitable Liquids Were Detected An Ignitable Liquid Is Detected We can look at this in four different ways... No ignitable liquids were ever used Ignitable liquids were used to start the fire, but have been totally consumed. Ignitable liquids are still present; however, not in the collected sample. Ignitable liquids are still present in the collected sample; however, they are too dilute to be detected. • “Sample contains a medium petroleum distillate (MPD), some examples are paint thinners and mineral spirits”. • “Sample contains a mixture of gasoline and a heavy petroleum distillate (HPD). Some examples of a HPD are diesel fuels and heating oils.”

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