Explosives Study Guide

Accelerant

A substance that speeds up and sustains fire, often used in arson.

Explosive

A material that produces a sudden release of energy, typically causing an explosion.

Oxygen Balance (OB)

A measure of whether an explosive compound has the right amount of oxygen to fully oxidize carbon and hydrogen.

Positive Oxygen Balance

Indicates excess oxygen in an explosive, which can help burn surrounding materials.

Negative Oxygen Balance

Indicates insufficient oxygen in an explosive, leading to incomplete combustion.

Isomers

Chemicals with the same formula but different structures, useful for identifying and differentiating substances.

Electronic Sniffer

An instrument that detects explosive molecules in the air by analyzing their presence.

Gas Chromatography-Mass Spectrometry (GC-MS)

A method used to analyze residues from explosives, identifying chemical components.

Plastic Explosives

Soft and malleable explosives, such as C-4, that can be easily shaped for specific targets.

TNT (Trinitrotoluene)

A stable high explosive, commonly used in military applications.

Dynamite

An explosive made from nitroglycerin absorbed in a stabilizing material; less stable than TNT.

Deflagration

A type of combustion that produces a shockwave traveling slower than sound.

Detonation

A type of explosion that generates a shock wave traveling faster than sound.

Low Explosives

Explosives that deflagrate at subsonic speeds, often used as propellants.

High Explosives

Explosives that detonate at supersonic speeds, causing significant damage.

Taggants

Micron-sized polymer chips added to explosives for detection purposes.

Chemical Signature

The specific chemical trace left behind by substances like accelerants or explosives.

Residue Analysis

The examination of leftover materials after an explosion to determine the type and source.

Neutron Activation Analysis (NAA)

A method used to detect elements in a sample by bombarding it with neutrons.

Thermal Analysis

Technique used to assess how a sample reacts when heated, helping detect explosives.

Accelerant vs. Explosive

An accelerant is a substance that enhances fire but does not explode, whereas an explosive is a material that undergoes a rapid reaction producing gas and an explosion.

Low Explosives vs. High Explosives

Low explosives burn at subsonic speeds (e.g., black powder), while high explosives detonate at supersonic speeds (e.g., TNT).

Components of Black Powder

Potassium nitrate, charcoal, and sulfur, which produce gases and heat upon combustion.

TNT vs. Dynamite

TNT is a stable explosive, while dynamite contains nitroglycerin and is less stable, making it more sensitive to shock.

Types of Bombs

Conventional bombs, nuclear bombs, and improvised explosive devices (IEDs).

Main Parts of a Bomb

Timer/switch, detonator, detonating cords, eboosters, main charge, electronic circuitry, and batteries/wires.

Determining Oxygen Balance

Calculating the amount of oxygen needed to completely oxidize the carbon and hydrogen in an explosive.

Methods for Detecting Explosives

Thermal analysis, neutron activation analysis, and chemical signature analysis.

Marker Compounds in Plastic Explosives

Added to plastic explosives for enhanced detection, helping identify the presence of explosives.

How X-Ray Scanners Work

They use ionizing radiation to create images of the contents of luggage, identifying dense materials like explosives.

Challenges with X-Ray Screening

Human error, not all things are in baggage, and substances can’t be detected

Methods for Detecting Non-Metallic Explosives

Gas chromatography and mass spectrometry for analyzing chemical residues.

Airline Passenger Screening Methods

Body scanners, metal detectors, and explosives trace detection systems.

ATF Crime Types

Arson, illegal trafficking of explosives, and firearm offenses.

Evidence Analyzed by Explosives Analysts

Examine residues, fragments, and chemical signatures from bombing incidents.

Procedure for Analyzing Explosion Evidence

Collecting samples, conducting chemical analysis, and comparing findings to known explosives.

Determining Chemical Composition of Residues

The chemical composition of residues helps identify the type of explosive used and potential sources.

Instruments for Examining Explosive Residue

Techniques like GC-MS separate and identify compounds in samples, detecting trace explosive residues, while infrared spectroscopy identifies chemical bonds and thermal analysis assesses reactions to heat.

Scanning Electron Microscope (SEM)

A type of microscope that uses focused beams of electrons to create high-resolution images of sample surfaces.

Energy-Dispersive X-ray Spectrometer (EDX/EDS)

An analytical technique attached to SEM that allows for the elemental analysis of the sample by detecting X-rays emitted from the material.

SEM-EDX

Enables the study of both the morphology and elemental composition of explosive residues.

Applications of SEM-EDX in Explosives Analysis

SEM-EDX is used to detect and analyze explosive residues, providing valuable information on the materials used in explosive devices.

Advantages of SEM-EDX

Offers high spatial resolution and the ability to analyze small sample sizes, essential for identifying trace explosive materials.