ArsonAnalysis 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. 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).

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. Ignition temp: The minimum temperature that will support or cause self-sustained combustion. Combustible materials have to be heated to their ignition temperature before they burn.

Ignition temperature and flash points are NOT related! Arson Investigation Definitions. Flammable liquid. Combustible liquid. Flammable. Flammable or explosive limits. Vapor density. Ignition temperature and flash points are NOT related! Liquid Flash Point Ignition Temp Gasoline -45oF 536oF to 853oF Kerosene 100oF 410oF A Flammable Liquid is any liquid having a flash point below 100oF. A Combustible Liquid is any liquid having a flash point above 100oF. Flammable means a combustible material that ignites very easily, burns intensely, or has a rapid rate of flame spread. Flammable or Explosive Limits is the extreme concentration limits of a combustible/flammable gas in air that a flame, once ignited, will continue to burn. Vapor Density is the ratio of weight of a volume of a given gas to an equal volume of dry air.

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.

Arson Investigation Point of Origin (POO). Interior Examination. 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. 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. Origin may be either exact point or a general area.

Arson Investigation

Accelerants Examples: Gasoline Kerosene Diesel Lighter fluids 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

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

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.

Steps to Recover and Identify Accelerants 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.

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

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. A gas chromatograph is coupled to a mass selective detector.

An Ignitable Liquid Is Detected No Ignitable Liquids Were 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.” 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.