Fire hose nozzles are specially designed appliances that deliver an optimal amount of water at a given rate of pressure. There are a variety of nozzles that come in different shapes and sizes. However, they all operate basically the same, using a simple shutoff valve to control the flow of water. Knowing which nozzle to use is dependent upon the type of fire and suppression needs at the scene.
Smooth bore nozzles are among some of the oldest types of nozzles used in the fire service. Aside from the shut-off valve, they contain no other parts. They use a tapered design and operate effectively at about 50 to 80 pounds per square inch. Unlike other types of nozzles, smooth bore nozzles provide a solid stream of water that is capable of penetrating through flames to directly attack what material is burning.
Fog nozzles are capable of producing anything from a wide dispersion pattern, similar to mist setting on a garden hose nozzle, to a straight stream of water. Unlike smooth bore nozzles, the introduction of air into the water column decreases penetration and the distance the stream of water can travel. These nozzles operate best between 80 to 100 psi. When used in its wide-dispersion setting, it is effective against propane fires because it creates a curtain of water that the fire cannot penetrate. In hydraulic ventilation, the fog pattern pulls air from behind it forward, pushing smoke out of an enclosed space.
Foam eductors are specially designed nozzles that are used to apply fire suppression foam. Unlike water, foam relies on its ability to cover an area and suffocate the fire by lying on top of the burning material. These nozzles are large, bell shaped cones and operate at a significantly lower amount of water pressure than smooth bore or fog nozzles.
Deluge guns are appliances that deliver water at a high rate of pressure. Because of their ability to supply water in large quantities -- upwards of 300 gallons per minutes -- they are also referred to as master streams. These can be mounted atop fire apparatus or fixed to aerial ladders.
Some nozzles are equipped with a wire mesh screen designed to catch large obstructions in the water supply. This screen should be checked after each use to make sure it is not blocked, reducing the flow of water through the nozzle. Nozzle shut-off valves should be firm, but not overly tight. Too tight makes them difficult to use. Check nozzle coupling "O" rings for wear periodically and replace as needed. These rubber rings are located right inside the coupling and help to create a seal between the hose and the nozzle to reduce leakage from the coupling.
- Essential of Firefighting and Emergency Response; T.R. Koonce, III; 2004
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