What foam application method should be used on open-top storage tank fires?

The bounce-off method is the appropriate choice for foam application on open-top storage tank fires because it effectively creates a blanket of foam that suppresses flames while minimizing the risk of igniting flammable vapors. In this technique, foam is projected onto the surface of the fire at an angle, allowing it to "bounce" off the surface and spread out to cover a larger area. This method is advantageous in open-top tank scenarios where direct application could lead to disturbing the burning material and potentially increasing the risk of explosion or flare-ups.

Using this technique allows for a safer and more controlled application that can prevent igniting vapors, as it does not disturb the liquid and minimizes the amount of heat affecting the intact material. It ensures better coverage of the fire environment, which is critical for controlling and extinguishing the fire effectively. Environmentally-friendly methods may focus on sustainability but may not address the immediate danger posed by the fire as effectively as the bounce-off method. The other methods, such as rain-down or roll-in, may not be as effective in this specific context, as they could disrupt the surface or fail to provide adequate coverage of the flames.