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Firefighter I Chemistry and Physics of Fire Slide 2 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. 2 Copyright and Terms of Service Copyright Texas Education Agency, 2011. These materials are copyrighted and trademarked as the property of the Texas Education Agency (TEA) and may not be reproduced without the express written permission of TEA, except under the following conditions: 1) Texas public school districts, charter schools, and Education Service Centers may reproduce and use copies of the Materials and Related Materials for the districts and schools educational use without obtaining permission from TEA. 2) Residents of the state of Texas may reproduce and use copies of the Materials and Related Materials for individual personal use only, without obtaining written permission of TEA. 3) Any portion reproduced must be reproduced in its entirety and remain unedited, unaltered and unchanged in any way. 4) No monetary charge can be made for the reproduced materials or any document containing them; however, a reasonable charge to cover only the cost of reproduction and distribution may be charged. Private entities or persons located in Texas that are not Texas public school districts, Texas Education Service Centers, or Texas charter schools or any entity, whether public or private, educational or non-educational, located outside the state of Texas MUST obtain written approval from TEA and will be required to enter into a license agreement that may involve the payment of a licensing fee or a royalty. Contact TEA Copyrights with any questions you may have.TEA Copyrights Slide 3 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. Fire/Combustion Defined Fire rapid, self-sustaining oxidation accompanied by heat and light in varying intensities Combustion a chemical reaction that releases energy as heat and usually light 3 Slide 4 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. Fire Triangle Fuel Heat (energy) Oxidizer (air) 4 Slide 5 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. Fire Tetrahedron Fuel Heat (energy) Oxidizer (air) Chemical Chain Reaction 5 Slide 6 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. Oxidizers Oxygen is the most common Occurs as 21% of air Increasing the amount of oxidizer may increase the intensity of the fire. 6 Slide 7 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. Oxidizers Other oxidizers: fluorine chlorine 7 Slide 8 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. Fuels Fuel Occurs in the three states of matter: Solid Liquid Gas State is often temperature-dependent To combine with oxidizer both MUST be in gaseous states Is vaporized by input heat in a process called pyrolysis 8 Slide 9 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. Fuels The most common fuels contain Carbon Hydrogen Complete combustion yields H 2 0 CO 2 Most combustion is incomplete producing Smoke CO 2 Other fire gases 9 Slide 10 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. Solid fuels As heat is added to solid fuels, the molecules are broken down into smaller components that vaporize and recombine with the oxidizer. When the fuel is hot enough to self-sustain combustion, it is at its ignition temperature. The size, arrangement, continuity, and moisture content of the solid fuel can affect the rate of pyrolysis. 10 Slide 11 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. Pyrolysis Pyrolysis a chemical change brought about by heat 11 Slide 12 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. Liquid Fuels Factors affecting liquid fuels Flow like water but do NOT readily separate Specific Gravity t he weight of the liquid compared to the weight of an equal volume of water Boiling Point w hen the vapor pressure equals atmospheric pressure 12 Slide 13 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. Liquid Fuels Volatility the ease at which the liquid gives off vapors at ambient temperatures Flash Point the minimum temperature at which a liquid gives off vapors sufficient to form an ignitable mixture with air Miscibility the ability of the liquid to mix with water 13 Slide 14 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. Gaseous Fuels Tend to expand indefinitely Flammable Limits/Flammable Range the fuel mixture can be too rich or too lean to burn Classification is flammable or nonflammable Some nonflammable gases support combustion (oxygen is an example) Flammable vapors are NOT always visible 14 Slide 15 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. Heat and Temperature Sources of heat energy Chemical Mechanical Electrical Nuclear 15 Slide 16 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. Heat and Temperature British Thermal Unit The amount of heat 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 16 Slide 17 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. Heat Transfer Three methods of heat transfer: Conduction through a medium without visible motion Convection through a circulating medium (liquid or gas) Radiation by wavelengths of energy Direct Flame Contact a combination of the three methods of heat transfer, as objects are bathed in flames 17 Slide 18 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. Classification of Fires Class A: ordinary combustibles Class B: flammable liquids (gases) Class C: energized electrical equipment Class D: flammable metals Class K: cooking materials (cooking oils/fats/grease) 18 Slide 19 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. Stages/Phases of Fire Incipient stage Oxygen at 21% Flame temperature 180 degrees F - 220 degrees F Heat has not spread to other fuels nearby Growth stage Early stage of a fire Availability of fuel and oxygen is unlimited Characterized by rapid increase of heat (temperature) 19 Slide 20 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. Stages/Phases of Fire Fully Developed Energy release is at a maximum rate and limited only by the availability of fuel and/or oxygen Decay When much of the fuel has been consumed Energy being released has diminished Temperature decreases Fire goes from ventilation-controlled to fuel- controlled 20 Slide 21 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. Stages/Phases of Fire 21 Slide 22 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. Related Terminology Flashover Phenomena in which all surfaces and objects in a fire have been heated to their ignition temperature and ignite Rollover/Flameover Phenomena where unburned gases accumulated at the top of a compartment ignite and flames spread across the ceiling 22 Slide 23 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. Related Terminology Backdraft An instantaneous explosion or rapid burning of superheated gases that occurs when oxygen is introduced into an oxygen-depleted space Signs of a possible backdraft Smoke stained window Yellow-grey smoke Little or no flame Smoke issuing from small cracks in puffs High heat levels 23 Slide 24 Copyright Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission. Resources 1418001775, Introduction to Fire Protection (3 rd Edition), Klinoff, Robert 0879392886, Essentials of Firefighting (5 th Edition), IFSTA 24