In CAFS exterior protection, which foam type and consistency is recommended?

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

Answer: (D)

In CAFS exterior protection, you want a foam that forms a lasting, adherent blanket on exposed surfaces to slow heat transfer and protect nearby exposures. Class A foam is designed for ordinary combustibles, making it the appropriate choice for exterior structure protection rather than Class B, which targets hydrocarbon fuels. The dry consistency is favored because it creates a lighter, more film-like coating that clings to vertical surfaces and resists rapid run-off, providing a durable protective layer without soaking the surface. This allows the cooling effect of the water and the insulating foam blanket to remain on the exterior longer, improving protection while reducing excess water that can cause runoff.