When approaching a burning flammable liquid vessel to operate the valve, which combination of hose streams should be used?

Using two 1¾" (45 mm) hose lines when approaching a burning flammable liquid vessel is an effective strategy because this combination allows for greater maneuverability and flexibility in a hazardous environment.

The flammable nature of the liquid makes the situation potentially very volatile, so having two hose lines ensures that there is a backup in case one line fails or if additional water volume is needed. Furthermore, the 1¾" hose diameter provides a balance between manageable weight and sufficient water flow to suppress the flames effectively. This size is easier for firefighters to handle, especially when they may need to move quickly to operate the valve or reposition due to changing fire conditions.

Selecting this option reflects an understanding of the need for adequate attack lines that can deliver enough water while also ensuring that firefighters can safely approach and operate near the fire, minimizing risk and enhancing the overall effectiveness of the suppression effort.