What's The Foam In A Foam Extinguisher?

There are two containers in the foam extinguisher. They are aluminum sulfate and sodium bicarbonate solutions. The two solutions are not in contact with each other and no chemical reaction occurs. When a foam fire extinguisher is needed, turn the fire extinguisher upside down and mix the two solutions together to produce a large amount of carbon dioxide gas:
Al2(SO4) 3 +6 NaHCO3 = = 3Na2SO4 +2Al(OH) 3 +6 CO2 
In addition to the two reactants, some blowing agents have been added to the fire extinguisher. Turn on the switch, foam is ejected from the fire extinguisher, and it is covered on the combustion object, so that the burning material is separated from the air and the temperature is reduced. To achieve the purpose of fire extinguishing, because foam fire extinguishers contain a lot of water, it is not as good as carbon dioxide liquid extinguishers.