Fire Behavior & Extinguisher Use

METHODS OF HEAT TRANSFER TS 2–7 Conduction — Point-to-point transmission of heat energy Convection — Transfer of heat energy by the movement of heated liquids or gasses Radiation — Transmission of energy as an electromagnetic wave without an intervening medium

CHEMICAL REACTIONS (cont.) TS 2–10b Oxidation — Formation of a chemical bond between oxygen and another element Instantaneous oxidation = Explosion Rapid oxidation = Fire (steady state or free-burning) Very slow oxidation = Rust

TYPES OF OXIDATION Instantaneous oxidation — Explosion TS 2–11 Instantaneous oxidation — Explosion Rapid oxidation — Fire (steady state or free-burning) Very slow oxidation — Rust

OXIDIZING AGENTS TS 2–12a Those materials that yield oxygen or other oxidizing gases during the course of a chemical reaction Oxygen rich atmospheres — Those with oxygen concentrations exceeding 21% Health care facilities Industrial occupancies Private homes (where occupants use liquid oxygen breathing equipment)

OXIDIZING AGENTS (cont.) TS 2–12b Oxygen deficient atmospheres — Those with oxygen concentrations lower than 21% Storage tanks Silos Pipes and vaults Other confined spaces High altitudes

FUEL CHARACTERISTICS TS 2–13a Fuel — Material or substance being oxidized or burned in the combustion process Pyrolysis — Chemical decomposition of a substance through the action of heat Surface-to-mass ratio — Surface area of fuel in relation to its mass Vaporization — Transformation of a liquid to its vapor or gaseous state

FUEL CHARACTERISTICS (cont.) TS 2–13b Flammable range — Range of concentrations of fuel vapor and air in which combustion will occur Lower flammable limit (LFL) — Minimum concentration of fuel vapor and air that supports combustion Upper flammable limit (UFL) — Concentration of fuel vapor and air above which combustion cannot take place

CHEMICAL HEAT ENERGY TS 2–14 Most common source of heat in combustion reactions Self-heating (spontaneous heating) — Chemical energy that occurs when a material increases in temperature without the addition of external heat Conditions that must be present for spontaneous ignition to occur Sufficient heat production Sufficient air supply Sufficient insulation

COMPARTMENT FIRE DEVELOPMENT TERMS TS 2–16 Compartment — Enclosed room or space within a building Compartment fire — Fire that occurs within a compartment Fuel controlled — Amount of fuel available to burn is limited Ventilation controlled — Amount of available oxygen is limited

GROWTH STAGE Plume development Plume begins to develop TS 2–18 Plume development Plume begins to develop Temperature of fire gases decreases as these gases move away from centerline of plume Development of ceiling layer Overall temperature in compartment increases Temperature of gas layer at ceiling increases

FLASHOVER STAGE TS 2–19a Transition between growth stage and fully developed fire stage; is not a specific event Preflashover condition — Radiant heat (red arrows in visual) from the hot ceiling gas layer heats combustible materials, producing vapors (green arrows in visual)

FLASHOVER STAGE (cont.) TS 2–19b Just prior to flashover — Temperatures rapidly increase Additional fuel packages become involved Fuel packages release combustible gases Flashover occurs when compartment temperature exceeds 900F (483C) and all combustible surfaces and gases are burning

FULLY DEVELOPED STAGE All combustible materials are involved in fire TS 2–20 All combustible materials are involved in fire Burning fuels release maximum amount of heat; produce large volumes of fire gases If fire becomes ventilation controlled, large volumes of unburned fire gases are likely to flow into adjacent spaces where they may ignite if air is more abundant

DECAY STAGE Heat release declines as available fuel is consumed TS 2–21 Heat release declines as available fuel is consumed Amount of fire diminishes Temperatures within compartment begin to decline Fuel is reduced to a mass of glowing embers

FACTORS THAT AFFECT FIRE DEVELOPMENT TS 2–22 Ventilation openings Size Number Arrangement Compartment volume Compartment’s thermal properties Ceiling height Initial fuel package Size Composition Location Additional target fuels Availability

FLAMEOVER / ROLLOVER TS 2–23 Condition where flames move through or across the unburned gases during a fire’s progression and roll across the ceiling Involves only fire gases, not the surfaces of other fuel packages (flashover)

THERMAL LAYERING OF GASSES TS 2–24 Thermal layering — Tendency of gases to form layers according to temperature Heat stratification — Hottest gases form top layers; cooler gases form bottom layers Thermal balance — No disruption of heat stratification Thermal imbalance — Disruption of heat stratification (hot gases mix throughout the compartment)

TEMPERATURE REDUCTION TS 2–25 Is used on solid fuels and liquid fuels with high flash points Is most common method of extinguishment Reduces temperature of high flash point fuels Creates negative heat balance Cools with water

FUEL REMOVAL Is used on solid, liquid, or gas fuels TS 2–26 Is used on solid, liquid, or gas fuels Stops flow of liquid or gaseous fuel Moves solid fuel out of fire path Allows fire to consume all fuel

OXYGEN EXCLUSION OR DILUTION TS 2–27 Is used on solid, liquid, or gas fuels Prevents air from reaching fuel (smothering) Dilutes or displacing oxygen with an inert gas

INHIBITION OF CHAIN REACTION TS 2–28 Is used on gas and liquid fuels Uses dry chemicals and halogenated hydrocarbons Interrupts chemical chain reaction (stops flaming)

Video Fire Behavior

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