Chapter 18: Fires and Explosives

Endothermic

A reaction that requires the input of energy in order for the reaction to take place.

Exothermic

A chemical reaction that releases energy as one of its products.

Accelerants

Fuels that are easily vaporized and support combustion, and are highly exothermic.

ANFO

Ammonium nitrate; pellets of it are coated with fuel oil.

Wildfires

________ are either natural or deliberate.

Conflagration

The spark from the spark plug causes a very rapid combustion to take place.

Mass spectrometry

________ has added flexibility and refinement to GC analysis of fire scene evidence.

Arson

Fires that are deliberately set with criminal intent.

Solid Phase Microextraction

A fiber made from fused silica is coated with an adsorbent such as charcoal or Tenax.

Vapor Trace Analyzer

A detector that help aid sifting through evidence to find explosive residues from the scene.

Class IIIA

Flash point at or above 140°F (60°C) and below 200 °F (93.4°C)

Flash point

The lowest temperature that will allow a liquid to produce a flammable vapor.

Class IC

Flash point at or above 73 °F (22.8°C) and below 100°F (37.8 °C)

detonator

The ________ may be a blasting cap or other suitable primary explosive.

Mechanical fires

It happens when a machine overheats either through misuse or incorrect placement.

Target Compound Analysis

A profile of compounds that are present in each type of accelerant, such as gasoline, are monitored by the mass spectrometer.

Natural Fires

Caused by lightning strikes; flammable gases that escape from the ground around an oil field and combust.

Active Adsorption

Two tubes containing charcoal or Tenax are inserted partway into the container through holes in the top.

Black powder

________ is a finely milled mixture of carbon, sulfur, and potassium nitrate.

Blast Pressure

The wave that is created by this blast will shatter anything that gets in its way.

Explosive trains

________ may contain as few as two steps or up to four or more.

Low explosives

________ can be easily set off by using a flame, a spark, or chemicals such as acids.

V Patterns

If the point of origin is near a wall or corner of a room, smoke damage on the wall (s) usually occurs in a "V "shape.

Electrical Fires

________ happens due to malfunction of wirings or overheating.

Arson dogs

________ are specially trained dogs that can sniff out trace evidence of hydrocarbon accelerants.

Combustion

The reaction of a fuel with oxygen.

Smoke

Occurs when there is incomplete combustion in a fire.

Electron Capture Detector

Used to detect the presence of explosive residues.

Direct Ignition

It involves direct application of a spark or flame source to the fuel.

fire tetrahedron

The ________ depicts the four elements that must be present in order to have a fire: a source of heat or energy, fuel, source of oxygen, and chain reaction between the fuel and oxygen.

Deliberate Fires

Started with malicious intent involves a number of steps.

Low Order Explosion

One that takes place at less than optimal efficiency.

Material distortion

Metal and glass may melt or distort owing to high heat.

Smokeless powder

________ consists of small particles containing nitrocellulose (single base) or nitrocellulose and NG (double base)

Flame point

The highest temperature.

Selective Ion Monitoring

The mass spectrometer looks for particular ions that are characteristic of particular types of flammables.

Neat ignitable liquid

It may be possible to pour off the liquid from the residue, filter it to remove solid particulates, separate the hydrocarbon from the water, and make a direct injection into the gas chromatograph.

Class IA

Flash point below 73°F (22.8°C) and boiling point below 100 °F (37.8°C)

Class IB

Flash point below 73°F (22.8°C) and boiling point at or above 100 °F (37.8 °C)

Class II

Flash point at or above 100 °F (37 °C) and below 140 °F (60°C)

Class IIIB

Flash point at or above 200 °F (93.4 °C)

Low Burning

Fires generally start in a low area of a building

Wood charring

The depth of wood charring depends upon the intensity of the heat near the wood and the time of exposure

Spalling

_________ is the destruction of a surface due to heat or other factors

Weathering

used to describe the degradation of an accelerant due to heat or other environmental factors

Headspace Methods

a technique for sampling and examining the volatiles associated with a solid or liquid sample

Passive Adsorption

a small container of charcoal or Tenax or a plastic strip coated with one of them is placed or suspended inside the container

Active Adsorption

two tubes containing charcoal or Tenax are inserted partway into the container through holes in the top

Solid Phase Microextraction

a fiber made from fused silica is coated with an adsorbent such as charcoal or Tenax

Solvent Extraction

an evidence container is opened and a small quantity of a suitable solvent is added

Steam Distillation

Some of the accelerant residue is put in a distillation apparatus with some water, which is then boiled and distilled

Target Compound Analysis

a profile of compounds that are present in each type of accelerant, such as gasoline, are monitored by the mass spectrometer

Conflagration

the spark from the spark plug causes a very rapid combustion to take place

Negative Pressure Phase

not as powerful as the positive pressure blast phase but it is capable of doing additional serious damage to objects that have already been damaged by the initial blast

Low Explosives

have detonation velocities below 3280 fps

High Explosives

have detonation rates above 3280fps

Low Explosive Trains

One example would be a pipe bomb wherein a fuse made of black powder is used to detonate smokeless powder inside the pipe

High Explosive Trains

The final explosive is usually a secondary explosive

spontaneous combustion

Sometimes rags that have been used to clean up spills from kerosene or another fuel can heat up enough to cause “______” if they are left in a closed area for a long time.