Arson and Explosives Midterm

Fire

A rapid oxidation process, which is a chemical rxn resulting in the evolution of light and heat in varying intensities; uncontrolled combustion

Explosion

The sudden conversion of potential energy into kinetic energy with the production and release of gases under pressure, or the release of gas under pressure

Fire Investigation

The formal process of determining the origin, cause, and development of a fire or explosion

Cause

Circumstances, conditions, or agencies that brought about or resulted in the fire or explosion incident, damage or bodily injury or loss of life resulting from the fire or explosion

Origin

The general location where a fire or explosion began

Arson

The crime of maliciously and intentionally, or recklessly, starting a fire or causing an explosion

Fire Signature

A fire development curve of time versus heat release rate typically having 4 phases of incipient ignition, growth, fully developed, and decay

Flashover

The transition phase in the development of a compartment fire is when surfaces exposed to thermal radiation reach ignition temperature more or less simultaneously, and fire spreads rapidly throughout the space, resulting in full room involvement, or total involvement, of the compartment or enclosed space.

Combustion

A chemical process of oxidation that occurs at a rate fast enough to produce heat and usually light in the form of either a glow or flame.

Pyrolysis

A process in which material is decomposed, or broken down, into simpler molecular compounds by the effects of heat alone.

Deflagration

Propagation of a combustion zone at a velocity that is less than the speed of sound in the unreacted medium.

Incendiary

A fire that is intentionally ignited in an area or under circumstances where and when there should not be a fire.

Accidental Fire

All fires for which the proven cause does not involve an intentional human act to ignite or spread fire into an area where it should not be.

Backdraft

A deflagration resulting from the sudden introduction of air into a confined space containing oxygen-deficient products of incomplete combustion.

Mechanical Explosion

An explosion where a container, vessel, or pipe bursts when internal gas or liquid pressures exceed the tensile strength of the container.

Fire Plumes

Buoyant column of hot gases produced by the combustion of a fuel source emitting a vertical column of flames, hot products of combustion, and smoke rising above a fire.

How is heat of a fire transferred to the ceiling above?

Convection - the heat naturally rises and becomes trapped when it hits the ceiling.

What are the four elements necessary to have a fire?

Oxygen, Fuel, Heat, Chain Reaction

What is the primary goal of a fire investigation?

To determine circumstances caused or contributed to the incident

How does a flashover occur?

Surfaces that are exposed to thermal radiation reach ignition temperature more or less simultaneously and results in full room involvement of the enclosed space

What temperature do flashovers occur at?

Upper-layer gases must be 600 degrees C or higher

How is heat transferred in conduction?

Energy is passed from one molecule to another through direct physical contact

What is required for a liquid to ignite?

Must reach its “flash point,” which is the minimum tempertature at which it produces enough vapor to form an ignitable mixture with the air, and hten be exposed to an ignition source

Flame Point

The lowest temperature at which a liquid produces a vapor that can sustain a continuous flame

Flash Point

The lowest temperature of a liquid, as determined by specific laboratory tests, at which the liquid gives off vapors at a sufficient rate to support a momentary flame across its surface.

Smoldering

Combustion without flame, usually with incandescence and smoke

Spontaneous Combustion

Due to self-heating, is a special form of smoldering ignition that does not involve an external heating process. An exothermic reaction within the material is the source of the energy that leads to ignition and burning.

Convection

Heat transfer by circulation within a medium such as a gas or a liquid

Indicators of a clandestine laboratory

A strong ammonia scent, Psuedophedrines, Lithium Batteries, Butane, Lye, Camping fuel or automotive fuel additive, muriatic acid, Iodine solution, Dimethyl sulfone, or corroded propane tanks

What is the role of a Fire Fighter at the scene of a fire?

Protect life and property (can serve as a witness as well)

3 safety changes implemented after the Iroquois Theater fire

Lighting of exits, panic bars, doors open to the outside

Blast Seat

A craterlike indentation created at the point of origin of some explosions