Abstract: Fire-fighting apparatus and the method of using of same in which water from a supply source is adapted to be pumped at high pressure and predetermined flow rates through a fire hose and in which metered quantities of a chemical foamant are injected into the fire hose and mixed with the water stream to increase the effectiveness of the mixture as a fire extinguishant. A special purpose computer module is configured to monitor the flow rate of the water through the hose, the level of chemical foamant in a supply reservoir and the speed of the positive displacement pump used to inject the foamant. The computer then determines an appropriate speed for the pump and provides a closed-loop control signal to the pump's drive motor to maintain a desired chemical injection rate.