Hydraulic ventilation is achieved by utilizing hose-lines with a nozzle set on a fog pattern that should cover about what percent of the window or door opening?

Hydraulic ventilation is a technique used by firefighters to clear smoke and heat from a structure following a fire. It employs water spray, typically with a fog nozzle, to create a pressure differential that draws smoke out of the building while replacing it with cooler air.

When executing hydraulic ventilation, the fog pattern needs to adequately cover a significant portion of the window or door opening to be effective. Covering about 90 percent of the opening allows for maximum airflow and efficiency in pulling out the smoke and heat. This extensive coverage ensures that the water droplets can interact with the air, creating a well-defined pressure flow that enhances the ventilation process.

By allowing 90 percent coverage, firefighters can effectively manage the smoke movement without creating unnecessary backflow or turbulence within the structure, which might hinder the evacuation of heat and smoke. Thus, focusing on such a large area bolsters the effectiveness of the hydraulic ventilation strategy, ensuring both safety and efficiency in firefighting operations.