Limits for divers carry tanks of the human body provide a breathing gas at ambient pressure to overcome. The tanks are also known as a cylinder or bottle and is usually in the recreational diving breathing gas is air. Some non-divers will move the tanks as oxygen tanks or bottles, but this is false - Oxygen is toxic if inhaled at high concentrations of oxygen in deep and pure is not used in recreational diving. The cylinders are almost always made of steel or aluminum, the latter the advantage of being corrosion resistant. While the original material is steel, which is widely used throughout Europe, it is customary to make aluminum bottles in the United States and the Caribbean.
Aluminum tanks suffer disadvantages, however - as it is softer than steel, it tends to be damaged by rough or careless treatment, and because the walls are thick to be bigger and heaver tanks needed during a comparable steel tank. However, if the tank suffers from internal corrosion of the oxide layer prevents further corrosion protect the tank - in a steel tank that is not the case.
Usually worn on the back of the divers, a bottle of compressed air to the BCD (BCD), or a jacket and attached to the top of the bottle is attached to the first step. The main port for the first stage, the terminal A, but less frequently seen in Europe, the option-Din connector - it provides a strong seal the terminal A.
The first stage regulator supplies air to the BCD - the air is released or expelled by the diver neutrally buoyant, chest varies with depth - and the air pressure gauge that is nowadays often included in a dive computer. It also provides air into the second stage, at an average pressure which is reduced by the second level of the ambient pressure to breathe diving. The standard configuration for the second step in modern diving equipment is in the same housing as the mouthpiece.
