Explanation
A soda acid fire extinguisher typically contains a solution of sodium bicarbonate (also known as sodium hydrogen carbonate) and an acid (sulfuric, tartaric etc) in separate compartments within the extinguisher.
To activate the extinguisher, a plunger or lever is pressed, which breaks a glass vial containing the acid solution, allowing it to mix with the sodium bicarbonate solution. The reaction between the two solutions produces carbon dioxide gas, which is released through a nozzle or hose to extinguish the fire.