Which class of foam employs the roll-on, bankdown, and rainbow methods for application?

Answer: B — Class B

The class of foam that employs the roll-on, bankdown, and rainbow methods for application is Class B foam. This type of foam is specifically designed for combating flammable and combustible liquids, such as gasoline and oils. The application techniques are crucial because they enhance the effectiveness of the foam by ensuring proper coverage and creating a barrier to smother the flames. The roll-on method involves rolling the foam directly onto the surface of the fire, which helps to displace the flammable liquid and cover the flames. The bankdown method is used to direct the foam over the edge of a burning surface, allowing it to flow down onto the fire, thus effectively covering it. The rainbow method, meanwhile, is utilized to create a visual indicator showing the foam as it is applied, which helps to ensure that the entire surface is treated effectively. Each of these methods is particularly well-suited to the liquid-fuel fires that Class B foam targets, underlining the importance of selecting the correct foam type and application technique to ensure fire suppression is successful.