How does Class A foam extinguish and/or prevent ignition?

Class A foam is specifically designed to enhance the effectiveness of water when combating fires involving ordinary combustibles such as wood, paper, and textiles. The primary mechanism through which Class A foam extinguishes and prevents ignition is by allowing water to penetrate fuels more effectively.

When applied to a fire, Class A foam reduces the surface tension of water, enabling it to spread and soak into the fuel rather than just running off the surface. This improved penetration enhances the ability of water to cool the fuel and extinguish the fire. By penetrating the materials, the foam helps to saturate them and can even assist in reducing the amount of combustible material available to sustain the fire, thus helping to control or eliminate the ignition potential.

This characteristic is vital in fire suppression scenarios, as it not only helps extinguish existing fires but can also aid in preventing re-ignition by ensuring that the fuel is adequately treated.