OC – Open Circuit

Open circuit is the breathing system most commonly used for scuba diving. It is called open circuit because all the gas exhaled by the diver is expelled in the environment. A basic OC breathing apparatus is composed of a cylinder, a regulator first and second stage and a pressure gauge. The other systems are called CCR for closed circuit rebreather or SCR for semi-closed rebreather because they reuse in a loop all or part of the diver exhaled gas.