In a CAFS setup to protect the exterior of structures, which combination and foam condition is effective?

In a CAFS setup to protect the exterior of structures, which combination and foam condition is effective?

• A. Class B foam; wet
• B. Class B foam; drier
• C. Class A foam; wet
• D. Class A foam; drier

Answer: (D)

CAFS exterior protection relies on a foam blanket that sticks to the surface and resists wind-driven runoff. Class A foam is the right choice for protecting structures because it forms a film suited to ordinary combustibles. Making the foam drier—lower water content with more air—produces a thicker, more durable blanket that clings to vertical surfaces and provides longer-lasting cooling and protection against radiant heat and embers. Wet foam would run off more easily and offer less lasting protection, and Class B foam is aimed at hydrocarbon fuels. So the most effective combination is Class A foam in a drier condition.

CAFS exterior protection relies on a foam blanket that sticks to the surface and resists wind-driven runoff. Class A foam is the right choice for protecting structures because it forms a film suited to ordinary combustibles. Making the foam drier—lower water content with more air—produces a thicker, more durable blanket that clings to vertical surfaces and provides longer-lasting cooling and protection against radiant heat and embers. Wet foam would run off more easily and offer less lasting protection, and Class B foam is aimed at hydrocarbon fuels. So the most effective combination is Class A foam in a drier condition.