Firefighter I Chemistry and Physics of Fire

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission. 2 Copyright and Terms of Service Copyright © Texas Education Agency, 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

Copyright © Texas Education Agency 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

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission. Fire Triangle Fuel Heat (energy) Oxidizer (air) 4

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission. Fire Tetrahedron Fuel Heat (energy) Oxidizer (air) Chemical Chain Reaction 5

Copyright © Texas Education Agency 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

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission. Oxidizers Other oxidizers: fluorine chlorine 7

Copyright © Texas Education Agency 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

Copyright © Texas Education Agency 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

Copyright © Texas Education Agency 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

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission. Pyrolysis Pyrolysis – a chemical change brought about by heat 11

Copyright © Texas Education Agency 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

Copyright © Texas Education Agency 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

Copyright © Texas Education Agency 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

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission. Heat and Temperature Sources of heat energy Chemical Mechanical Electrical Nuclear 15

Copyright © Texas Education Agency 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

Copyright © Texas Education Agency 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

Copyright © Texas Education Agency 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

Copyright © Texas Education Agency 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 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

Copyright © Texas Education Agency 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

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission. Stages/Phases of Fire 21

Copyright © Texas Education Agency 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

Copyright © Texas Education Agency 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

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), IFSTA 24