Fire Extinguishment Theory FIREFIGHTER I 1

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Key Terms Fire – a rapid, self-sustaining oxidation process accompanied by the evolution of heat and light 3 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Key Terms (continued) Combustion – a chemical reaction that releases energy as heat and usually light. When a substance is undergoing combustion, it is usually referred to as being “on fire.” 4 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Key Terms (continued) Oxidation – the chemical combination of any substance with an oxidizer Oxidizer – a substance that gains electrons in a chemical reaction Energy – the capacity for doing work 5 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Fire Triangle 6 Originally, fire was thought to be based on the presence of three elements: Fuel Air Heat Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Fire Triangle (continued) 7 From a scientific standpoint the three elements should be: Fuel Oxidizer (air) Energy (heat) Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Fire Triangle (continued) 8 Fires in a smoldering mode of combustion can be extinguished or controlled by removing one of the three elements. Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Fire Tetrahedron 9 There is a fourth component called a chemical chain reaction. Molecules are broken down by heat, producing free radicals. Free radicals combine with the oxidizer. The process produces more heat and more free radicals, and the process continues. As long as there are ample amounts of fuel, oxidizer, and energy, the combustion process continues until it is interrupted. Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Fire Tetrahedron (continued) 10 Firefighters must recognize the four planes of a Tetrahedron: Reducing agent (fuel) Oxidizing agent (oxygen) Energy (heat) Chemical chain reaction Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Fuel Removal 11 Eliminating the fuel source effectively extinguishes any fire. Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Fuel Removal (continued) 12 Eliminating the fuel source can be accomplished by Allowing the fire to burn until all the fuel is consumed Shutting off or removing the source of the fuel supply Closing a valve (liquid or gaseous fuels) Removing solid fuels in the path of the fire (i.e. wildland fires) Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Oxygen Exclusion 13 Removing or reducing available oxygen from the combustion process will reduce a fire’s growth, and in most cases, extinguish the fire over time. Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Oxygen Exclusion (continued) 14 Some examples of oxygen removal are Placing a cover on a pan of burning grease Using a carbon dioxide (CO 2 ) extinguisher to displace the oxygen in a confined space and disrupt the combustion process Using a foam blanket to separate flammable liquids from the atmosphere None of the above methods will work with fuels that are self-oxidizing. Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Temperature Reduction The temperature of the fuel must be reduced to a point where the fuel ceases to produce flammable vapors. The most common method of temperature reduction used to extinguish or control fires is cooling the fire with the application of water. Cooling with water is the most effective method available for use on smoldering fires. 15 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Temperature Reduction (continued) Water must be applied in sufficient amounts to absorb the heat being generated by the combustion process. Cooling with water cannot sufficiently reduce the amount of vapors produced in fires involving low flashpoint flammable liquids and gases. 16 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Temperature Reduction (continued) Water has its greatest cooling effect when it is vaporized and converted into steam. Water expands to 1700 times its original volume when converted to steam at 212 degrees Fahrenheit (F). Beware: excess steam production can make the situation less tenable for firefighters by making it more difficult to see, and increasing the chances of steam burns. 17 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Water Expansion 18 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Chemical Flame Inhibition These interrupt the combustion process by limiting the production of free radicals: Some extinguishing agents including some dry chemical extinguishers Some halogenated agents (halons) New replacement agents 19 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Chemical Flame Inhibition (continued) Chemical flame inhibition is Most effective on fires in the flaming mode of combustion, such as gaseous and liquid fuel fires Less effective on fires in the smoldering mode of combustion, to the point that the concentration of extinguishing agent necessary and the amount of time involved makes the attempt impractical. 20 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Extinguishing Properties of Water Water can extinguish fire in different ways: 1. By cooling (heat absorption) 2. By smothering, diluting, or excluding oxygen 3. By heat absorption (converting into water vapor or steam) 21 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Extinguishing Properties of Water (continued) Water is readily available and is inexpensive (relatively). has a greater heat absorbing capacity than most other common agents. changing into steam requires a relatively large amount of heat (latent heat of vaporization). 22 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Extinguishing Properties of Water (continued) Water when converted to steam Absorbs more heat faster, and cools the fuel below its ignition temperature. The steam displaces hot gases, smoke, and other products of combustion. In some cases, the steam smothers the fire through oxygen exclusion. 23 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Extinguishing Properties of Water (continued) 24 Water can be applied in many different ways: Solid stream Fog stream Straight Narrow pattern Wide pattern Broken stream Water can be used as a cooling agent for protecting exposures. Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Law of Specific Heat Specific heat – the amount of heat needed to raise the temperature of a specific mass of a substance 1 degree. Water has a high specific heat (greater heat-absorbing capacity) than most other common extinguishing agents. BTU/British Thermal Unit – the amount of temperature needed to raise the temperature of 1 pound of water by 1 degree Fahrenheit Calorie – the amount of heat needed to raise the temperature of 1 gram of water by 1 degree Celsius 25 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Law of Latent Heat Latent heat – the amount of energy it takes to melt or boil a certain amount of material A pound of water will absorb 1 BTU for every degree F it is raised, until it reaches its boiling point (212 degrees F). An additional 970 BTUs as it is completely converted to steam (latent heat of vaporization). 26 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

A gallon of water will absorb 8.33 BTUs for every degree F it is raised, until it reaches its boiling point (212 degrees F). an additional 8,080 BTUS as it is completely converted to steam (latent heat of vaporization). Because of its ability to absorb heat, water is a very effective extinguishing agent. 27 Law of Latent Heat (continued) Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Law of Heat Flow The second law of thermodynamics Heat flows from a hot substance to a cold substance, but not the other way around. When you put ice in a warm glass of water, the water melts the ice. When it snows, the warm ground will melt the snow. When water is applied to a fire, the heat of the fire raises the temperature of the water being applied. 28 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Advantages of Using Water as an Extinguishing Agent Availability Affordability Effectiveness Easily stored Can be transported long distances 29 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Disadvantages of Using Water as an Extinguishing Agent Water is relatively heavy; it weighs 8.33 pounds per gallon. Directing master streams into buildings can result in heavy accumulations of water in the structure, increasing the potential for structural collapse. Water and water-based extinguishing agents cannot safely be used on Class C fires until the electrical energy has been eliminated. Water applied to a combustible metal fire can result in a violent reaction that could intensify the combustion process. 30 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.

Resources , Introduction to Fire Protection (3 rd Edition), Klinoff, Robert , Essentials of Firefighting (5 th Edition), International Fire Service Training Association (IFSTA) Images used with permission by IFSTA. 31 Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.