Table A: Fires are grouped into classes by fuel types

Class A FiresFueled by wood, paper, cloth, plastics, rubber.
Class B FiresFueled by flammable and combustible liquids, greases, gases.
Class C FiresFueled by energized electrical equipment.
Class D FiresFueled by combustible metals such as magnesium, sodium, potassium, titanium, zirconium.

Table B: General Definition

ConductionTransfer of heat by direct contact with the material, such as a metal fire poke in a fire or a pot in contact with a gas flame on a stove.
ConvectionOccurs when the density of liquids and gases is reduced, causing them to expand and rise on heat transfer.
RadiationCauses the radiative transfer of heat until the vaporized or pyrolized fuel is ignited by the flames.
Direct Flame ContactThe hot gases and flames from the reaction come into contact with the fuel.
Flash PointThe lowest temperature at which a liquid gives off sufficient vapour to form a mixture with air that will support combustion.
PyrolysisFor a solid, the phase change from a solid to a gas by heat alone. With as little as 8% oxygen, smoldering and charring is observed.

Table B: Fire and Combustion

Flame PointThe temperature a few degrees above the flash point is necessary to produce sufficient vapors to sustain a flame.
Fire TetrahedronIncludes the features of the fire triangle (heat, oxygen, fuel) and adds a fourth variable—an uninhibited chain reaction.
Fire SuppressionBased on controlling or removing one of the components of the fire tetrahedron (heat, oxygen, fuel, uninhibited chain reaction).
Flammable MaterialsMaterials capable of burning with a flame and have a flashpoint of less than 37.8°C (100°F). Examples include gasoline, propane, acetylene, and hydrogen.
Combustible MaterialsLiquids with a flashpoint above 37.8°C (100°F) and can burn under ambient temperature and pressure.
Spontaneous CombustionOccurs in poorly ventilated containers or areas as a result of a natural heat-producing process when appropriate proportions of fuel and oxygen are present.
Glowing CombustionBurning at the fuel–air interface or surface without producing a flame, typically due to insufficient heat to pyrolyze the fuel.

Reference: Introduction to Forensic Chemistry by Kelly M. Elkins.

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