A valve includes an inlet to allow gas to enter the valve; an overpressure system to provide an overpressure; and a reclaim outlet to allow gas from the valve to exit the valve. Optionally, the reclaim outlet can connect to a reclaim system or a dump system which can be used for recovering the gas flowing through the valve.

A gas negative pressure valve is provided which comprises a valve body and a valve cover. A gas inlet and a gas outlet are disposed on the valve body. A drive lever and a diaphragm assembly are disposed inside the valve body, and one end of the drive lever is connected to a lower end of the diaphragm assembly, and the other end of the drive lever is connected with a sealing gasket. An end of the drive lever is hinged on a sidewall of the valve body. A reset spring is disposed between the drive lever and a bottom of an inner chamber of the valve body. A guide passage is opened in the inner chamber of the valve body. An end of the drive lever close to the gas inlet is connected with a guide shaft, a lower end of which is cooperated slidably in the guide passage.

A second stage regulator suitable for both right-handed and left-handed divers includes a housing, a mouthpiece, a decompression mechanism, an exhaust mechanism and an airflow adjustment mechanism. The airflow adjustment mechanism can control the output air volume by adjusting the size of the vent. Even in the state of small air volume, the diver only needs to inhale a little to push the second stage output and inhale the air smoothly. The diver can control the direction of the airflow by operating the airflow adjustment mechanism to avoid being choked by the air when the air volume is large. The exhaust holes of the exhaust mechanism is arranged on the side and the exhaust mechanism is facing the left rear side of the housing, which can prevent the exhaust valve from being compressed due to the pressure of water flow when the diver is swimming.

A pressure-reducing system for a breathing apparatus including: i) a supply conduit for supplying a pressurised breathable gas; ii) a suction mouthpiece for a user to breathe in the breathable gas; and iii) a valve operatively interposed between the supply conduit and the suction mouthpiece. The valve includes: an inlet, an outlet; a shutter permits or prevents the passage of the breathable gas from the inlet to the outlet; anda pressure balancing chamber, the shutter being interposed between the inlet of the valve and the balancing chamber; the shutter defining a conduit that places the inlet of the valve and the pressure balancing chamber in fluid communication. The pressure-reducing system further includes iv) a movement system for moving the pressure balancing chamber towards the inlet for the breathable gas to push the shutter from the first position to the second position.