Chapter 6 Glossary - Fire Behavior

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Atom

Back 1

The smallest particle of an element, which can exist alone or in combination.

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Backdraft

Back 2

A phenomenon that occurs when a fire takes place in a confined area, such as a sealed aircraft fuselage, and burns undetected until most of the oxygen within is consumed. The heat continues to produce flammable gases, mostly in the form of carbon monoxide. These gases are heated above their ignition temperature and when a supply of oxygen is introduced, as when normal entry points are opened, the gases could ignite with explosive force. (NFPA 402)

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Black fire

Back 3

A hot, high-volume, high-velocity, turbulent, ultra-dense black smoke that indicates an impending flashover or autoignition.

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Boiling liquid/expanding vapor explosion (BLEVE)

Back 4

An explosion that occurs when a tank containing a volatile liquid at the bottom of the tank and a flammable gas at the top of the tank is heated to the point where the tank ruptures.

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Box

Back 5

A burning structure.

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Chemical energy

Back 6

Energy that is created or released by the combination or decomposition of chemical compounds.

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Class A fire

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A fire in ordinary combustible materials, such as wood, cloth, paper, rubber, and many plastics. (NFPA 10)

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Class B fire

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A fire in flammable liquids, combustible liquids, petroleum greases, tars, oils, oil-based paints, solvents, lacquers, alcohols, and flammable gases. (NFPA 10)

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Class C fire

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A fire that involves energized electrical equipment. (NFPA 10)

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Class D fire

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A fire in combustible metals, such as magnesium, titanium, zirconium, sodium, lithium, and potassium. (NFPA 10)

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Class K fire

Back 11

A fire in a cooking appliance that involves combustible cooking media (vegetable or animal oils and fats). (NFPA 10)

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Combustion

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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 a flame. (NFPA 101)

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Compartment

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A space completely enclosed by walls and a ceiling. The compartment enclosure is permitted to have openings in walls to an adjoining space if the openings have a minimum lintel depth of 8 inches (203 mm) from the ceiling and the openings do not exceed 8 feet (2.44 m) in width. A single opening of 36 inches (914 mm) or less in width without a lintel is permitted when there are no other openings to adjoining spaces. (NFPA 13)

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Conduction

Back 14

Heat transfer to another body or within a body by direct contact. (NFPA 921)

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Convection

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Heat transfer by circulation within a medium such as a gas or a liquid. (NFPA 921)

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Decay phase

Back 16

The phase of fire development in which the fire has consumed either the available fuel or oxygen and is starting to die down.

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Electrical energy

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Heat that is produced by electricity.

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Endothermic

Back 18

Reactions that absorb heat or require heat to be added.

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Exothermic

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Reactions that result in the release of energy in the form of heat.

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Fire

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A rapid, persistent chemical reaction that releases both heat and light.

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Fire tetrahedron

Back 21

A geometric shape used to depict the four components required for a fire to occur: fuel, oxygen, heat, and chemical chain reactions.

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Fire triangle

Back 22

A geometric shape used to depict the three components of which a fire is composed: fuel, oxygen, and heat.

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Flame point (fire point)

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The lowest temperature at which a substance releases enough vapors to ignite and sustain combustion.

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Flameover (rollover)

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The condition where unburned fuel (pyrolysate) from the originating fire has accumulated in the ceiling layer to a sufficient concentration (i.e., at or above the lower flammable limit) that it ignites and burns; it can occur without ignition of, or prior to, the ignition of other fuels separate from the origin. (NFPA 921)

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Flammability limits (explosive limits)

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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.

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Flash point

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The minimum temperature of a liquid at which sufficient vapor is given off to form an ignitable mixture with the air, near the surface of the liquid or within the vessel used. (NFPA 30)

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Flashover

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A transition phase in the development of a compartment fire in which 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. (NFPA 921)

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Fuel

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A material that will maintain combustion under specified environmental conditions. (NFPA 53)

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Fully developed phase

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The phase of fire development in which the fire is free-burning and consuming much of the fuel.

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Gas

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A material that has a vapor pressure greater than 300 kPa absolute (43.5 psia) at 50°C (122°F) or is completely gaseous at 20°C (68°F) at a standard pressure of 101.3 kPa absolute (14.7 psia). (NFPA 30A)

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Growth phase

Back 31

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.

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Hypoxia

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A state of inadequate oxygenation of the blood and tissue sufficient to cause impairment of function. (NFPA 99B)

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Ignition phase

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The phase of fire development in which the fire is limited to the immediate point of origin.

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Ignition temperature

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Minimum temperature a substance should attain to ignite under specific test conditions. (NFPA 921)

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Laminar smoke flow

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Smooth or streamlined movement of smoke, which indicates that the pressure in the building is not excessively high.

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Liquid

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Any material that (1) has a fluidity greater than that of 300 penetration asphalt when tested in accordance with ASTM D 5, Standard Method of Test for Penetration of Bituminous Materials , or (2) is a viscous substance for which a specific melting point cannot be determined but that is determined to be a liquid in accordance with ASTM D 4359, Standard Test for Determining Whether a Material Is a Liquid or a Solid. (NFPA 30)

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Lower flammable limit (LFL)

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That concentration of a combustible material in air below which ignition will not occur; also known as the lower explosive limit (LEL). Mixtures below this limit are said to be “too lean.” (NFPA 329)

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Matter

Back 38

A substance made up of atoms and molecules.

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Mechanical energy

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Heat that is created by friction.

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Oxidation

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Reaction with oxygen either in the form of the element or in the form of one of its compounds. (NFPA 53)

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Plume

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The column of hot gases, flames, and smoke rising above a fire; also called convection column, thermal updraft, or thermal column. (NFPA 921)

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Pyrolysis

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The destructive distillation of organic compounds in an oxygen-free environment that converts the organic matter into gases, liquids, and char. (NFPA 820)

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Radiation

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The emission and propagation of energy through matter or space by means of electromagnetic disturbances that display both wave-like and particle-like behavior. (NFPA 801)

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Smoke

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The airborne solid and liquid particulates and gases evolved when a material undergoes pyrolysis or combustion, together with the quantity of air that is entrained or otherwise mixed into the mass. (NFPA 318 )

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Smoke color

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The attribute of smoke that reflects the stage of burning of a fire and the material that is burning in the fire.

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Smoke density

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The thickness of smoke. Because it has a high mass per unit volume, smoke is difficult to see through.

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Smoke velocity

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The speed of smoke leaving a burning building.

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Smoke volume

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The quantity of smoke, which indicates how much fuel is being heated.

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Solid

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One of the three phases of matter; a material that has three dimensions and is firm in substance.

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Thermal column

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A cylindrical area above a fire in which heated air and gases rise and travel upward.

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Thermal layering

Back 51

The stratification (heat layers) that occurs in a room as a result of a fire.

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Thermal radiation

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The means by which heat is transferred to other objects.

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Turbulent smoke flow

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Agitated, boiling, angry-movement smoke, which indicates great heat in the burning building. It is a precursor to flashover.

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Upper flammable limit (UFL)

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The highest concentration of a combustible substance in a gaseous oxidizer that will propagate a flame. (NFPA 68)

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Vapor density

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The weight of an airborne concentration (vapor or gas) as compared to an equal volume of dry air.

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Volatility

Back 56

The ability of a substance to produce combustible vapors.