The soda-acid type fire extinguisher is the most commonly used fire extinguisher.
It is made up of a container, a small bottle and a knob. When the knob is struck, the bottle containing sulphuric acid breaks and reacts with sodium bicarbonate solution present in the container producing carbon dioxide gas. This gas when sprayed over fire forms a blanket around the fire cutting off the air supply, thus extinguishing  the fire.