Fire and Explosives

Arson Investigation

The process of investigating fires that are suspected to be intentionally set, often involving complex circumstances and planning by the perpetrator.

Oxidation

The chemical process of combining oxygen with other substances to produce new substances, such as in the case of fire.

Energy

The ability of a system to do work, which can take various forms such as heat and light.

Combustion

The process of starting and sustaining a fire, requiring the presence of fuel, oxygen, and sufficient heat.

Physical state of the fuel

The state in which a fuel must be in order to achieve a reaction rate with oxygen sufficient to produce a flame, such as gaseous for most fuels.

Heat Transfer

The movement of heat energy through conduction, radiation, or convection.

Conduction

The transfer of heat through a solid object, with poor conductors known as insulators.

Radiation

The transfer of heat energy by electromagnetic radiation, which can cause surfaces to burst into flames when reaching the ignition temperature.

Convection

The transfer of heat energy by the movement of molecules within a liquid or gas, such as hot gases rising in a structural fire.

Fire Scene

The area where a fire has occurred, which must be examined by arson investigators for signs of arson.

Flashover

The occurrence when all combustible fuels in a structure simultaneously ignite, engulfing the entire structure.

Searching for Accelerants

The process of searching for traces of flammable liquid residues, often aided by portable vapor detectors or "sniffers."

Collection of Fire Scene Evidence

The collection and storage of ash, soot, and porous materials suspected of containing accelerants in airtight containers for laboratory analysis.

Gas Chromatography

A sensitive and reliable laboratory technique used to detect and characterize flammable residues, separating hydrocarbon components to identify the accelerant used.

Explosions

Rapid oxidation reactions that produce large quantities of gases, classified as high or low explosives.

Low Explosives

Explosives like black powder and smokeless powder that deflagrate, causing the container walls to fragment and fly outward.

High Explosives

Explosives that detonate rapidly, producing a supersonic shock wave and outward rush of gases, requiring a primary explosive to initiate.

Military and Peroxide Explosives

Military explosives like RDX and homemade explosives like TATP, which can be made using acetone and peroxide.

Collection and Analysis

The systematic search and collection of debris and objects from explosion sites for laboratory examination, using techniques like ion mobility spectrometry and gas chromatography/mass spectrometry.

Confirmatory Identification

Additional tests performed on unexploded materials, such as infrared spectrophotometry, to confirm the presence of explosives.