Pressure Reducing Second Stage for Underwater Use

A pressure reducing second stage for underwater use includes a case provided with a breathing gas inlet, with an inhalation/exhalation port and with an exhaled gas exhaust outlet with a non-return valve, the gas inhalation/exhalation port being connected to a mouthpiece tube, the breathing gas inlet in the case being connected to a breathing gas pressure reducing device provided with a hollow cylindrical element or pipe, which has a breathing gas inlet port communicating with a gas supply conduit through a valve which is interposed between the supply conduit and the mouthpiece tube, the case being provided with a pressure sensitive means device for controlling the opening/closure of the valve. The breathing gas inlet in the case is provided in its lower portion and the hollow cylindrical element is connected to the inlet on the case such that its axis is substantially vertical, when used in the upright position.