Abstract: A method for extinguishing fires in aircraft cargo spaces includes two pressure chambers separated by an annular boss which houses a restricting orifice and a check valve assembly. A lower chamber acts as a high rate discharge fire extinguisher and the upper chamber acts as a metering fire extinguisher. Upon receipt of an activation command from the cockpit, all the agent contained in the high rate discharge chamber is emptied within seconds. At the same time, the pressurized agent contained in the upper chamber pushes the check valve to a closed position and allows the agent in the metering chamber to flow through the orifice of the restrictor at a predetermined rate. With the properly sized orifice, the agent in the upper chamber will be emptied at a rate that lasts for the needed duration of the aircraft fire protection system.