What is the appropriate foam percentage ratio for hydrocarbons when using Class B foam?

The appropriate foam percentage ratio for hydrocarbons when using Class B foam is 3%. This percentage is essential for effectively suppressing flammable liquid fires, particularly those that involve hydrocarbons like gasoline and diesel.

Class B foams are specifically designed to form a barrier on the surface of burning liquids, preventing oxygen from reaching the flames and suppressing vapors that can ignite. The 3% solution is optimal because it ensures sufficient coverage and foam expansion, leading to effective fire suppression.

Using a concentration that is too low may not provide the necessary protective barrier, while a concentration that is too high can lead to excess foam production, making it difficult to manage and control the situation. Therefore, the 3% foam ratio strikes the right balance, allowing firefighters to efficiently extinguish the fire while minimizing the risk of flare-ups or re-ignition.