Which factor is MOST likely to affect the degree of expansion in a foam solution?

The degree of expansion in a foam solution is primarily influenced by the rate at which the foam is applied. When applying foam, the higher the rate of application, the more air is entrained into the foam. This results in greater expansion as the foam solution mixes with air during the application process. A rapid application can create a more voluminous foam blanket, which is critical for effectively suppressing fires.

While the type of foam concentrate, water temperature, and mixing ratio are all important factors in the overall performance and effectiveness of foam, they do not directly determine the degree of expansion in the same way that the rate of application does. The type of foam concentrate might affect the bubble structure and stability, and the mixing ratio is significant for ensuring proper foam characteristics, but it is the application technique that predominantly drives expansion. Therefore, the factor that most significantly impacts the degree of expansion in a foam solution is indeed the rate at which it is applied.