Firefighting, Structural Firefighting

Exterior Water Application: Influence of Nozzle Positioning and Pressure

Issue 5 and Volume 173.

By Pablo J. Boj García External water application (EWA) is a suppression technique performed from the outside of a structure fire. Its objective is to improve the conditions inside a fire compartment by taking away some of the energy the fire is developing, thus “resetting” it to a previous, less-intense condition. Water has a cooling effect when projected into the burning enclosure even if it does not reach the seat of the fire. Water, however, is most effective in reducing the heat-release rate of the fire if it reaches the fuels that are burning instead of just cooling noncombustible walls and ceilings. The most significant factors influencing the dispersion of fire streams within a compartment are the position of the nozzle firefighter in relation to a window and the nozzle pressure.1 Considering these factors, a fire stream with adequate flow and relatively low velocity applied at a steep angle will…

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