What was previously thought to be crucial for the extinguishing action of carbon dioxide in foam?

The reasoning behind the belief that carbon dioxide presence was crucial for the extinguishing action of foam lies in the role carbon dioxide plays in fire suppression. Initially, it was understood that foam extinguished fires by smothering the flames, effectively cutting off the oxygen supply needed for combustion. In this context, carbon dioxide was seen as a key component, as it can displace oxygen in the environment surrounding a fire.

Foam creates a barrier between the fuel and the atmosphere, which includes oxygen. With the prevalence of carbon dioxide, it was presumed to facilitate the effectiveness of this barrier, thereby enhancing oxygen exclusion. This illustrates why carbon dioxide presence was emphasized as a critical element in the extinguishing process.

As fire behavior and suppression strategies have been studied more thoroughly, it has become clear that while carbon dioxide presence aids in the process, the primary action of foam lies more in its ability to form a blanket over the fuel, rather than relying solely on the presence of carbon dioxide itself for extinguishment. This shift in understanding highlights the complexity of fire suppression agents and the mechanisms by which they operate.