If a large pool of flammable liquid is burning in an open area, what foam application method may be the most effective?

In the scenario of a large pool of flammable liquid burning in an open area, the rain down method is appropriate because it allows for the foam to be applied in a manner that creates a gentle and even coating over the burning surface. This technique promotes foam expansion and coverage, effectively smothering the flames by forming a blanket over the combustible material.

The rain down method is particularly useful for large volumes of fire because it helps to ensure that the foam reaches all areas of the burning liquid, providing a more uniform distribution that can help prevent reignition and control the fire quickly.

Using other methods, such as a direct stream, may not provide adequate coverage for a large pool fire, and the aggressive application could potentially displace the burning liquid or create a spray that could ignite nearby materials. Surround and drown typically works better for contained fires and can be less effective in an open area. The foam blanket technique is highly effective but relies on the foam being delivered in a way that allows it to float on top of the flammable liquid, which could be better suited for certain types of applications rather than widespread rain down-style coverage.