Objectives

• Define "fire."
• Know the three sides of the fire triangle.
• Explain the methods of heat movement.
• List the stages of fire behavior.
• List the four sides of the fire tetrahedron.
• Describe four classifications of fire.

• Fire
• Electricity
• Wheel

• Fire is a chemical process.
• Fire is also known as combustion.
• Fire is a rapid, self-sustaining oxidation process.

• Oxidation
• Temperature
• Latent heat of fusion
• Latent heat of vaporization
• Exothermic reaction
• Endothermic reaction
• Carbon dioxide
• Carbon monoxide
• Oxidizers

• Oxygen
• Heat
• Fuel

• The air normally contains approximately 21% oxygen, 78% nitrogen.
• If the atmosphere is such that a fire cannot burn, it cannot support life.

• Ignition temperature
• Flashover
• Heat sources
• Friction
• Pyrophoric reaction

• Radiation
• Conduction
• Convection

• Heat is radiated from a burning fire in all directions.
• The rays travel in any direction and continue to move in that direction until their energy is dissipated.

• When two materials having different temperatures are placed in contact with one another, the material having the greatest heat will transmit some of it to the material having the least heat.

• Convected heat moves in air currents.
• Convected heat is the culprit in multiple-story fires.
• Many times the drafts are induced by firefighters in their ventilation procedures.

• Flammable limits are expressed as a percentage of a vapor/air mixture.
• Flash point
• Fire point
• Explosive limits

• Fires generally start small and continue to grow until one of the sides of the fire tetrahedron begins to disappear.

• Ignition stage
• Growth stage
• Flashover stage
• Fully developed stage
• Decay stage

• This is the beginning stage. In this stage the four elements later described for a tetrahedron will come together to ignite the combustible material, and combustion will begin.

• During this stage the fire will quickly start consuming more material as the chain-reaction process takes place.
• The speed of the growth and ultimate size of the fire will primarily depend upon how much burnable material or fuel is available.

• The flashover stage is a transition stage that exists between the growth of a fire and a fully developed fire.
• A flashover does not take place in every fire.

• This stage occurs when all combustible materials within the perimeter of the fire’s boundaries are involved in the fire.
• During this stage the burning materials are releasing the maximum amount of heat possible.

• The temperature of the fire will begin to decline as the available oxygen or available fuel is used up.
• The fire will use up more and more of the oxygen as it continues into the decay stage in a closed room.

• There are three phenomena of the fire triangle that should be thoroughly understood by every firefighter. The cause of each is different, but the overall result is almost identical—all are potential killers.

• The first phenomenon is referred to as a backdraft.
• A backdraft occurs when the fuel side and the heat side of the triangle are in proper proportions in an area and the oxygen side is suddenly supplied.

• The second phenomenon is referred to as a flashover.
• The two sides of the fire triangle that are present in the proper proportions immediately before a flashover occurs are the oxygen side and the fuel side.

• A third phenomenon of the fire triangle is referred to as a rollover.
• The phenomenon is called this because the resultant fire manifests itself in a rolling motion, normally at ceiling level and ahead of the main fire, sometimes by as much as 10 to 20 feet.
• It is caused by the smoke at the ceiling level suddenly igniting as a result of being heated to its ignition temperature.

• The fire triangle was used to discuss the theory of fire.
• It was explained that it is necessary to have all three sides of the fire triangle present in the proper portions and the chain reaction in order to have a fire.
• Time has proven that there is more to it than that.

• The fire tetrahedron is a four-sided figure that incorporates the fire triangle and the added feature of the chain reaction.
• A fire may be extinguished by removing any side of the fire triangle or by breaking the chain reaction.

• The heat side of the fire tetrahedron is removed by the reduction of the temperature of the fire.
• The fuel side is removed by the removal of the fuel.
• The oxygen side is removed by the expulsion of the oxygen.
• The chain reaction side is removed by the breaking of the chain reaction.

• Fires have been classified by type primarily for the purpose of identifying the type of material required for extinguishment and what extinguisher to use on each type of fire.

• These are fires involving ordinary combustible material such as wood, paper, and cloth.

• These are fires involving flammable liquids, gases, and greases.

• These are fires involving energized electrical equipment.

• These are fires involving combustible metals such as magnesium, titanium, sodium, and potassium.

• These are fires involving cooking oils.

• Class A fires are generally extinguished by removing the heat side of the fire tetrahedron.
• Water is most often used, not only because of its availability, but also because of the characteristics of its composition.

• The ability of an extinguishing agent to absorb heat is referred to as its specific heat, thermal heat, or heat capacity.
• The expansion ratio is approximately 1,700 to 1 at a normal atmospheric pressure of 14.7 psi and a temperature of 212°F.

• Wet water is water to which an additive has been introduced in order to reduce the surface tension of the water.

• There has been some confusion circulating as to whether Class A foam is a retardant, a surfactant, or a wetting agent.
• Class A foam is a foam that has been specially designed for use on Class A combustibles.
• Class A foam can be applied by an eductor or by a compressed air foam system (CAFS).

• High-expansion foam consists of masses of air or carbon dioxide bubbles dispersed in water.
• High-expansion foams have an expansion ratio as high as 1,000 to 1 and are used in the extinguishment of fires in ordinary combustibles.

• Extinguishment takes place by breaking the chain reaction and by the decomposition of the agent, which leaves a sticky residue on the burning material.
• The sticky residue in effect assists in the extinguishing process by eliminating the oxygen side of the fire tetrahedron through the formation of a seal between the burning material and the air.

• Class B fires are generally extinguished by removing the oxygen side of the fire tetrahedron or by breaking the chain reaction.

• Dry chemicals are powders that are formed by grinding dry crystals and adding substances that will cause the powder to flow easily.
• Although it is known that smothering and radiation shielding contribute to the extinguishment of the fire, the quickness with which flames are eliminated suggests that the principal factor in extinguishment is the breaking of the chain reaction.

• Carbon dioxide is a nontoxic, noncorrosive, nonconductive, colorless, tasteless, odorless gas.
• Carbon dioxide is effective on both Class B and Class C fires.
• Carbon dioxide should be discharged above and directly on the fire.

• Fire fighting foams are produced by mixing a foam concentrate with water in the proper concentrations.
• Foams are defined by their expansion ratio.
• Air foams that are designed to extinguish Class B fires are not effective for use on flammable liquid fires involving fuels that are water soluble, water miscible, or "polar solvents."

• This foam is more commonly referred to as "A triple F."
• It is an extremely effective foam and is the foam recommended for extinguishing fires in hydrocarbon fuels.

• This foam is widely used in protecting fuel tanks and petroleum processing facilities.
• It has unique qualities that make it desirable for subsurface injection.

• In open containers of class B fires, foam should be applied by projecting the foam stream to the far side of the container and allowing it to cascade over the burning liquid.
• Spill fires in the open should be attacked by directing the foam stream on the surface in front of the fire, which will push the foam blanket over the fire.

• Class C fires are those involving energized electrical equipment.
• Once the equipment is de-energized, the fire becomes a Class A or Class B fire and can be handled accordingly.
• There is no available extinguishing agent for use on Class C fires only.

• Class D fires are those involving combustible metals.
• These metals are magnesium, sodium, potassium, uranium, titanium, lithium, thorium, hafnium, zirconium, and plutonium.
• No extinguisher or material is effective on all the different types of metals.

• Understanding fire behavior is important to the firefighter.
• How and why fire behaves the way that it does can help determine the best way to extinguish it.
• The firefighter who learns about how fire behaves is better equipped to fight it.