Firefighter I

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Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission. Physical Characteristics Of Water Solid – ice at 32° F (0° C) Liquid – between 32° and 212° F (0° – 100° C) Gas – invisible water vapor at 212° F or 100° C 3

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission. Physical Characteristics Of Water (continued) Weighs 8.33 pounds per gallon Expands to 1700 times its original volume when converted to steam at 212° F 4

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission. Law of Specific Heat The measurement of the heat absorbing capacity of a substance Water is noncombustible and can absorb large amounts of heat Heat absorbed by water spray (fog) causes the hot gas layer to contract in an indirect attack in a compartment fire 5

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission. Law of Latent Heat Latent heat – the amount of heat energy absorbed or released during a change of state (solid liquid gas) Latent Heat of Vaporization – the energy that is required to change a substance from a liquid state to a gaseous state 6

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission. Law of Heat Flow The 2nd law of thermodynamics – heat flows spontaneously from a hot to a cold body For heat to be transferred, the two bodies must be at different temperatures Heat moves from warm or hot objects to cooler objects The rate at which the heat transfer occurs is dependent on the temperature difference between the two objects conductivity of the materials involved the greater the difference, the greater the transfer rate 7

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission. Advantages of Water as an Extinguishing Agent Readily available and considered inexpensive Has greater heat absorbing capability (higher specific heat) than most common extinguishing agents Takes a relatively large amount of heat to completely convert to steam (high latent heat of vaporization) 8

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission. Advantages of Water as an Extinguishing Agent (continued) Used in many different forms or ways: – As a solid stream – As a broken stream – From a fog nozzle – Straight stream – Narrow pattern fog stream – Wide pattern fog stream 9

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission. Disadvantages of Water as an Extinguishing Agent High surface tension Can react readily with some materials like combustible metals Allows radiant heat to pass through it Freezes at 32° F or 0° C Conducts electricity readily 10

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission. Disadvantages of Water as an Extinguishing Agent (continued) Class D fires involve combustible metals that water readily reacts with if it’s used as an extinguishing agent 11

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission. Summary Water can extinguish fire in various ways. Primarily water is used to cool by absorbing heat. Water can also smother a fire by diluting or eliminating oxygen and thwarting the combustion process Through the vaporization process, water absorbs heat as it is converted to steam. 12

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission. Resources , Essentials of Firefighting (5 th Edition), International Fire Service Training Association (IFSTA) Images used with permission by IFSTA. 13