A fixed installation designed to displace the oxygen in the protected space and thus extinguish the fire, usually used to fight fires in engine rooms, boiler rooms, pump rooms and holds. The system normally consists of a series of large CO2 cylinders. The CO2 is supplied from the cylinder manifold to suitable points with diffusing nozzles. The discharge valve is located in a locked cabinet. Opening the cabinet activates an alarm to give personnel time for evacuation. Since the effectiveness of fixed CO2 fire fighting system diminishes the longer the fire burns, the speed is essential if CO2 is to be effective.