Important Definitions Related to Fundamental of Combustion and Fire

Table A: Fires are grouped into classes by fuel types

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

Table B: General Definition

Concept	Definition
Conduction	Transfer 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.
Convection	Occurs when the density of liquids and gases is reduced, causing them to expand and rise on heat transfer.
Radiation	Causes the radiative transfer of heat until the vaporized or pyrolized fuel is ignited by the flames.
Direct Flame Contact	The hot gases and flames from the reaction come into contact with the fuel.
Flash Point	The lowest temperature at which a liquid gives off sufficient vapour to form a mixture with air that will support combustion.
Pyrolysis	For 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

Concept	Definition
Flame Point	The temperature a few degrees above the flash point is necessary to produce sufficient vapors to sustain a flame.
Fire Tetrahedron	Includes the features of the fire triangle (heat, oxygen, fuel) and adds a fourth variable—an uninhibited chain reaction.
Fire Suppression	Based on controlling or removing one of the components of the fire tetrahedron (heat, oxygen, fuel, uninhibited chain reaction).
Flammable Materials	Materials 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 Materials	Liquids with a flashpoint above 37.8°C (100°F) and can burn under ambient temperature and pressure.
Spontaneous Combustion	Occurs 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 Combustion	Burning 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.