Which method is not effective for applying foam on certain types of fires?

The method referred to as "rain down" is not effective for applying foam on certain types of fires, particularly those involving flammable liquids or polar solvents. In scenarios where rapid suppression is necessary, applying foam in a manner that allows it to rain down can lead to insufficient coverage and penetration of the foam blanket over the burning fuel. This method may allow the burning liquid to reignite or burn through the foam.

In contrast, techniques like "bank in," which involves directing the foam onto a solid object or surface so it flows down to the fire, and "bounce off," where the foam is directed to bounce off an object and then land on the fire, help ensure that the foam maintains effective contact with the burning surface. The "spray evenly" method ensures that the foam is distributed consistently across the fire surface, creating a more effective barrier against reignition. Each of these methods is designed to optimize foam usage, ensuring it can blanket the fire effectively and suppress combustion.