Chapter 18: Firefighting, Rescue and Assistance
Applying Water E.1. Applying water
E.1.a. Straight (solid) stream
On board Coast Guard vessels, water for firefighting comes from a builtin fire pump through the fire main and hose system. You apply water to a fire using one of 3 ways: •
Straight (solid) stream
•
High-velocity fog
•
Low-velocity fog
A straight solid stream of water is used when long reach and penetrating power are critical. On Class A fires, its primary purpose is to break up burning material and to penetrate the base of a flame. Therefore, you must direct a solid stream at the base of flames in a Class A fire. A solid stream of water is not effective for extinguishing Class B fires. It can cause a violent fire reaction if a water stream atomizes fuel into the air causing an increased surface area. A straight solid stream can also be used on Class D fires for cooling and to wash burning materials over the side. A straight solid stream of water should not be used on a Class C fire because it is a conductor of electricity and, therefore, could be hazardous to a firefighting team.
E.1.b. Highvelocity fog
High-velocity fog is more useful than a solid stream on Class A fires. One reason is that high-velocity fog can cool a much wider surface than a steady stream and consequently, it can absorb more heat. Additionally, as fog comes into contact with any surface heated by fire, it becomes steam. Steam provides a secondary smothering effect which further aids in extinguishing the fire. Because of the cooling qualities of finely divided water particles, you can use high-velocity fog successfully on Class B fires. You should use highvelocity fog on flammable liquids only when Aqueous Film-Forming Foam (See Section F.2) is not available.
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