Which statement about Class A foam is true?

• A. It raises the surface tension of water.
• B. It lowers the surface tension of water, allowing better penetration into the fuel.
• C. It increases the fuel's flash point.
• D. It has no effect on water properties.

Answer: (B)

Class A foam primarily works as a wetting agent that lowers water’s surface tension. By reducing surface tension, the foam-water mix spreads and soaks into porous, ordinary-combustible fuels more effectively, reaching hidden pockets and cooling the fuel from within. This improved wetting helps form a stable foam blanket on the surface, sealing off air and slowing or stopping the flame, which also reduces the risk of reignition. It doesn’t raise surface tension; it lowers it. It also doesn’t change the fuel’s flash point—flash point is a property of the fuel itself, not something foam alters. So the statement that Class A foam lowers surface tension and enhances penetration into the fuel best describes its effect.