High and Low Pressure CO2 System CO2 systems are used as total flooding systems in engine rooms, machinery spaces and cargo holds. The HP system consists of a number of CO2 cylinders, whose outlets are connected to a common manifold. From there, the CO2 is directed, via selector valves, into the various protected spaces. If the protected space is large, a high number of cylinders are required. These can be replaced by a single CO2 tank, saving approximately 50% in weight and installation costs. The tank contains CO2 cooled to -18 °C. The tank, refrigerators, distribution valves, controls, etc., are supplied pre-wired and ready assembled on a steel frame.