Abstract: The disclosure herein describes a system for extinguishing fires which consists in first maintaining a supply of liquid fire extinguishing medium in a tank under a pressure cushion of expellant material; the medium is delivered upon detection of a hazard by opening a normally closed valve in a delivery line connected to the tank; this operation triggers a sequential operation of a plurality of groups of expellant containers which causes additional expellant material to be delivered to the tank to maintain therein a given pressure so as to effect quick and total evacuation of the fire extinguishing medium from the tank to the hazard.