When a vertical surface is near or within the area of a pool of ignitable liquid, which foam application technique may be employed?

• A. Direct spray method
• B. Blank down method
• C. Roll-on method
• D. Bank-down method

Answer: (B)

Blank down is chosen when a vertical surface is near or within a hydrocarbon pool because it creates a solid foam blanket on the vertical face. By directing foam onto the wall at a low angle, you establish a continuous protective layer that adheres to the vertical surface and then runs down to cover the pool edge. This blanket cools the fuel, reduces vapor release, and provides a barrier between the liquid and the air, helping prevent ignition and spreading of the fire along the vertical exposure. Other methods focus more on spraying foam over the surface, rolling foam onto horizontal areas, or letting foam bank and cascade down, which are less effective for establishing a stable, vertical foam barrier near the pool.