The chemical fire engine is fitted with two tanks, one of which contains a solution of bicarbonate ot soda and the other sulphuric acid. By allowing the acid to flow into the bicarbonate, carbonic acid is evolved, and the pressure induced forces the liquid through the hose pipe. When the liquids are mixed there is present a solution containing sulphate of soda holding carbonic acid in solution, and this has been found very effectual in putting out fires.