Aqueous film forming foam agents extinguish a fire by which method?

Aqueous film forming foam (AFFF) agents extinguish fires through a combination of cooling and smothering methods. When the foam is deployed, it creates a blanket that covers the burning surface. This film serves to smother the fire by sealing off the fuel from oxygen in the air, which is essential for combustion. Additionally, the foam has cooling properties; the water content in the foam absorbs heat from the fire, which helps lower the temperature and can effectively bring an end to the combustion process.

The combination of these two actions—cooling and smothering—makes AFFF effective for fighting liquid fuel fires, particularly hydrocarbon fires where oxygen supply is a significant factor in sustaining the fire. By effectively managing both the heat and the oxygen available to the fire, AFFF is able to quench flames and prevent re-ignition, which is crucial in firefighting scenarios.