The rate of application for Class B foam depends on:

• A. whether the fuel is spilled or contained in a tank
• B. the ambient temperature
• C. wind speed
• D. the brand of foam concentrate

Answer: (A)

The rate at which Class B foam is applied is determined by the configuration of the fuel surface you’re fighting. If the fuel is spilled on the ground or burning on an open surface (a pool fire), you need to blanket a large area quickly to suppress vapors and cooling the fuel, so you apply foam at a higher rate to cover the entire surface efficiently. If the fuel is contained in a tank, the surface area is smaller and confined, and the foam can be introduced inside the tank to blanket that liquid surface, so the required rate is lower. Other factors like temperature, wind, or foam brand can affect performance, but the primary factor shaping application rate is whether the fuel is an open spill versus a contained tank fire.