Which foam application method is used for blank down near vertical surfaces?

• A. Direct application at high pressure
• B. Roll-on technique
• C. Blank down method
• D. Fog curtain application

Answer: (C)

When you want to cover a vertical or nearly vertical surface with foam, you aim to form a continuous, adherent blanket rather than a heavy jet or a drifting spray. The blank down method is designed to lay down a broad foam layer that clings to the wall, cooling it and smothering vapors to prevent heat transfer and flame spread along the surface. This approach creates a stable foam blanket on the vertical face, which is exactly what you need for blanketing near vertical surfaces.

Direct application at high pressure tends to hit the surface with a strong jet rather than create a uniform blanket. The roll-on technique focuses foam along surfaces by rolling it on, which isn’t as effective for vertical faces that require a complete, vertical-surface blanket. Fog curtain application aims to form a protective veil to control heat and vapors, not to blanket a vertical surface with a cohesive foam layer.