Which of the following is a property of Aqueous Film Form Foam?

The property of Aqueous Film Forming Foam (AFFF) that makes it particularly effective in firefighting is its ability to create a vapor barrier when applied to burning liquids. This vapor barrier is crucial because it helps to prevent the release of flammable vapors from the surface of the burning liquid, effectively limiting the potential for flashback and helping to extinguish the fire more effectively.

When AFFF is deployed, it forms a film that spreads across the surface of the liquid, which not only suppresses the flames but also reduces the chances of re-ignition. This unique property is what distinguishes AFFF from other firefighting agents, enabling it to perform particularly well in scenarios involving hydrocarbon fuels.

Regarding the other answer choices, it’s important to clarify that AFFF does not primarily function as a repellent to water, nor is it designed specifically for biodegradability; these properties are not the key characteristics. Additionally, while AFFF can be effective against certain types of fires, it is not specifically intended for flammable gas fires, as its primary use is in liquid fuel fires.