Essentials of firefighting Chapter 4 fire dynamics key terms with verified correct definitions

asphyxiation Fatal condition caused by severe oxygen deficiency and an excess of carbon monoxide and/or other gases in the blood. autoignition Initiation of combustion by heat but without a spark or flame. autoignition temperature ( AIT) The lowest temperature at which a combustible material ignites in air without a spark or flame. Backdraft Instantaneous explosion or rapid burning of superheated gases that occurs when oxygen is introduced into an oxygen-depleted confined space. The stalled combustion resumes with explosive force; may occur because of inadequate or improper ventilation procedures. buoyant the tendency or capacity of a liquid or gas to remain afloat or rise carbon-based fuels Fuels in which the energy of combustion derives principally from carbon; includes materials such as wood, cotton, coal, or petroleum. Carbon Dioxide Colorless, odorloess heavier than air gas that neither supports combustions nor burns carbon monoxide ( CO) Colorless, odorless, dangerous gas ( both toxic and flammable) formed by the incomplete combustion of carbon Ceiling Jet horizontal movement of a layer of hot gases and combustions by-products from the center point of the plume, when a horizontal surface such as a ceiling redirects the vertical development of the rising plume chemical flame inhibition Extinguishment of a fire by interruption of the chemical chain reaction. 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. combustion zone Area surrounding a heat source in which there is sufficient air available to feed a fire. compartmentation The way that the arrangement of compartments creates or does not create a series of barriers designed to keep flames, smoke, and heat from spreading from one room or floor to another. conduction physical flow or transfer of heat energy from one body to another, through direct contact or an intervening medium, from the point where the heat is produced to another locartion, or from a region of high temps to a region of low temperature convection the transfer of heat by the movement of heated fluids or gases, usually in an upward direction endothermic reaction chemical reaction in which a substance absorbs heat energy capacity to perform work entrain to draw in and transport solid particles or gases by the flow of a fluid entrainment The drawing in and transporting of solid particles or gases by the flow of a fluid. exothermic reaction chemical reaction between two or more materials that changes the materials and produces heat exposure fire A fire ignited in fuel packages or buildings that are remote from the initial fuel package or building of origin. fire point Temperature at which a liquid fuel produces sufficient vapors to support combustion once the fuel is ignited. The fire point is usually a few degrees above the flash point. fire tetrahedron Model of the four elements/conditions required to have a fire. The four sides of the tetrahedron represent fuel, heat, oxygen, and chemical chain reaction. Fire triangle Plane geometric model of an equilateral triangle that is used to explain the conditions/elements necessary for combustion. The sides of the triangle represent heat, oxygen, and fuel. Flammable (Explosive) Range The range between the upper flammable limit and lower flammable limit in which a substance can be ignited. flash point Minimum temperature at which a liquid gives off enough vapors to form an ignitable mixture with air near the liquid's surface. flashover A rapid transition from the growth stage to the fully developed stage. flow path The space between at least one intake and one exhaust outlet. The difference in pressure determines the direction of the flow of gases through this space. Heat and smoke in a high pressure area will flow toward areas of lower pressure. free radical electronically charged, highly reactive parts of molecules released during combustion reactions fuel load The total quantity of combustible contents of a building, space, or fire area, including interior finish and trim, expressed in heat units of the equivalent weight in wood. heat of combustion Total amount of thermal energy (heat) that could be generated by the combustion (oxidation) reaction if a fuel were completely burned. The heat of combustion is measured in British Thermal Units (Btu) per pound or Megajoules per kilogram. heat flux The measure of the rate of heat transfer to a surface, expressed in kilowatts heat release rate Total amount of heat released per unit time. The heat release rate is typically measured in kilowatts (kW) or Megawatts (MW) of output. hydrocarbon fuel Petroleum-based organic compound that contains only hydrogen and carbon. hydrogen cyanide Colorless, toxic, and flammable liquid until it reaches 79 degrees. Above that temperature, it becomes a gas with a faint odor similar to bitter almonds; produced by the combustion of nitrogen-bearing substances. incomplete combustion Result of inefficient combustion of a fuel; the less efficient the combustion, the more products of combustion are produced rather than burned during the combustion process. isolated flames Flames in the hot gas layer that indicate the gas layer is within its flammable range and has begun to ignite; often observed immediately before a flashover. joule unit of energy kinetic energy energy possessed by a moving object because of its motion lower explosive flammable limit ( LEL) Lower limit at which a flammable gas or vapor will ignite and support combustion; below this limit the gas or vapor is too lean or thin to burn (lacks the proper quantity of fuel). Also known as Lower Flammable Limit (LFL) miscible materials that are capable of being mixed in all proportions neutral plane level at a compartment opening where there is an equal difference in pressure exerted by expanision and buoyancy of hot smoke flowing out of the opening and the inward pressure of cooler, ambient temperature air flowing in through the opening open burning description of a fire burning in the open with no restrictions to its oxygen supply oxidation any material that readily yields to oxygen or other oxidizing gas, or that readily reacts to promote or initate combustion of combustible materials piloted ignition Moment when a mixture of fuel and oxygen encounters an external heat (ignition) source with sufficient heat or thermal energy to start the combustion reaction. polar solvents Flammable liquids that have an attraction for water, much like a positive magnetic pole attracts a negative pole; examples include alcohol, ketone, and lacquer. potential energy stored energy possessed by an object that can be released in the future to perfomr work once released products of combustion Materials produced and released during burning.