Atom
The smallest particle of an element, which can exist alone or in combination.
Backdraft
The sudden explosive ignition of fire gases when oxygen is introduced into a superheated space previously deprived of oxygen.
Black fire
A hot, high-volume, high-velocity, turbulent, ultra-dense black smoke that indicates an impending flashover or autoignition.
Boiling liquid, expanding vapor explosion (BLEVE)
An explosion that occurs when a tank containing a volatile liquid is heated.
Box
A burning building.
Chemical energy
Energy that is created or released by the combination or decomposition of chemical compounds.
Class A fires
Fires involving ordinary combustible materials such as wood, cloth, paper, rubber, and many plastics.
Class B fires
Fires involving flammable and combustible liquids, oils, greases, tars, oil-based paints, lacquers, and flammable gases.
Class C fires
Fires involving energized electrical equipment where the electrical conductivity of the extinguishing media is of importance.
Class D fires
Fires involving combustible metals such as magnesium, titanium, zirconium, sodium, and potassium.
Class K fires
Fires involving combustible cooking media such as vegetable oils, animal oils, and fats.
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 flames.
Conduction
Heat transfer to another body or within a body by direct contact.
Convection
Heat transfer by circulation within a medium such as a gas or a liquid.
Decay phase
The phase of fire development in which the fire has consumed either the available fuel or oxygen and is starting to die down.
Electrical energy
Heat that is produced by electricity.
Endothermic
Reactions that absorb heat or require heat to be added.
Exothermic
Reactions that result in the release of energy in the form of heat.
Fire
A rapid, persistent chemical reaction that releases both heat and light.
Fire tetrahedron
A geometric shape used to depict the four components required for a fire to occur: fuel, oxygen, heat, and chemical chain reactions.
Fire triangle
A geometric shape used to depict the three components of which a fire is composed: fuel, oxygen, and heat
Flame point (fire point)
The lowest temperature at which a substance releases enough vapors to ignite and sustain combustion.
Flameover (rollover)
A condition in which unburned products of combustion from a fire have accumulated in the ceiling layer of gas to a sufficient concentration (i.e., at or above the lower flammable limit) such that they ignite momentarily.
Flammability limits
The upper and lower concentration limits (at a specified temperature and pressure) of a flammable gas or vapor in air that can be ignited, expressed as a percentage of the fuel by volume.
Flashover
The condition in which all combustibles in a room or confined space have been heated to the point at which they release vapors that will support combustion, causing all combustibles to ignite simultaneously.
Fuel
All combustible materials. The actual material that is being consumed by a fire, allowing the fire to take place.
Fully developed phase
The phase of fire development in which the fire is free-burning and consuming much of the fuel.
Gas
One of the three phases of matter. A substance that will expand indefinitely and assume the shape of the container that holds it.
Growth phase
The phase of fire development in which the fire is spreading beyond the point of origin and beginning to involve other fuels in the immediate area.
Hypoxia
A state of inadequate oxygenation of the blood and tissue.
Ignition phase
The phase of fire development in which the fire is limited to the immediate point of origin.
Ignition temperature
The minimum temperature at which a fuel, when heated, will ignite in air and continue to burn.
Laminar smoke flow
Smooth or streamlined movement of smoke. It indicates that the pressure in the building is not excessively high.
Liquid
One of the three phases of matter. A nongaseous substance that is composed of molecules that move and flow freely and that assumes the shape of the container that holds it.
Lower flammable limit (LFL)
The minimum amount of gaseous fuel that must be present in the air for the air/fuel mixture to be flammable or explosive.
Matter
Made up of atoms and molecules.
Mechanical energy
Heat that is created by friction.
Oxidation
A chemical reaction initiated by combining an element with oxygen, resulting in the formation of the element or one of its compounds.
Plume
The column of hot gases, flames, and smoke that rises above a fire. Also called a convection column, thermal updraft, or thermal column.
Pyrolysis
The chemical decomposition of a compound into one or more substances by heat alone. This often precedes combustion
Radiation
The combined process of emission, transmission, and absorption of energy traveling by electromagnetic wave propagation between a region of higher temperature and a region of lower temperature.
Smoke
An airborne particulate product of incomplete combustion that is suspended in gases, vapors, or solid or liquid aerosols.
Smoke color
The attribute of smoke that reflects the stage of burning of a fire.
Smoke density
The thickness of the smoke. Because it has a high mass per unit volume, smoke is hard to see through.
Smoke velocity
The speed of the smoke leaving a burning building.
Smoke volume
The quantity of smoke, which indicates how much fuel is being heated.
Solid
One of the three phases of matter. A substance that has three dimensions and is firm in substance.
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A cylindrical area above a fire in which heated air and gases rise and travel upward.
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The stratification (heat layers) that occurs in a room as a result of a fire.
Thermal radiation
How heat transfers to other objects
Turbulent smoke flow
Agitated, boiling, angry-movement smoke, which indicates great heat in the burning building. It is a precursor to flashover.
Upper flammable limit (UFL)
The maximum amount of gaseous fuel that can be present in the air for the air/fuel mixture to be flammable or explosive.
Vapor density
The weight of an airborne concentration (vapor or gas) as compared to an equal volume of dry air.
Volatility
The ability of a substance to produce combustible vapors.
Heat
Into what form is mechanical energy converted when two materials rub against each other and create friction?
By displacing oxygen
Though not itself toxic, carbon dioxide can still injure people. How?
Just a few seconds
How long, if at all, can a fire fighter in full protective gear survive flashover?
At the ceiling
In an enclosed room with a fire in it, where are the highest temperatures
The ignition phase
What is the starting point of a fire called?