What happens to the solution in a foam extinguisher when it is placed under pressure?

When a foam extinguisher is placed under pressure, the solution inside converts to foam when it is discharged. This process occurs due to the expansion of gases and the agitation of the liquid, which helps to trap air and form bubbles. The resulting foam effectively smothers flames by cutting off the supply of oxygen and cooling the fire. The formation of foam is essential to the extinguisher's function, as it creates a blanket that adheres to the burning surface and prevents re-ignition.

This attribute is what distinguishes foam extinguishers from other types of extinguishers. Other answers do not accurately describe what happens to the solution in a foam extinguisher when under pressure. The solution does not evaporate or revert back to a liquid; it continuously remains as a foamy blanket upon ejection. The cooling effect is a result of the extinguishing process itself but is not the direct consequence of pressurization.