Open-circuit regulators are of the type where exhaled air is vented from the system. Most common scuba sets work using an open circuit.
A closed-circuit regulator is used in rebreathers. This is because a rebreather scrubs and recycles air, making maximum use out of a small amount of gas.
The first stage is the part that is attached to the air cylinder. The first and most important valve, which controls the pressure at which compressed gas is released from the cylinder, is located here.
One of the hoses from the first stage is usually connected to a pair of gauges. The first is a pressure gauge that indicates the current depth of the diver, while the other is an indicator of how much air is remaining in the cylinder.
The demand valves are used for breathing and take the form of either mouthpieces or enclosed face masks. There are usually two: one for the diver, plus a second emergency demand valve.
Most regulators have one more hose, which is for the buoyancy control device (BCD). This is usually a vest with an air bladder inside it, which can be inflated (using air from the cylinder) and deflated to adjust a diver's buoyancy.
Article Written By Edwin Thomas
Edwin Thomas has been writing since 1997. His work has appeared in various online publications, including The Black Table, Proboxing-Fans and others. A travel blogger, editor and writer, Thomas has traveled from Argentina to Vietnam in pursuit of stories. He holds a Master of Arts in international affairs from American University.