Types
Modern scuba sets are of two types:
- open-circuit (examples are those invented in 1864 by Rouquayrol and Denayrouze, in 1926 by Yves le Prieur or the Aqua-Lung invented to extend duration with a demand regulator in 1942/43 by Jacques Yves Cousteau and Émile Gagnan). Here the diver breathes in from the equipment and all the exhaled gas goes to waste in the surrounding water. This type of equipment is relatively simple, making it cheaper and more reliable. The two-hose design originally used was the one designed by Cousteau and Gagnan. The single-hose design generally used today was invented in Australia by Ted Eldred. In Britain it for a long time was often called an "aqualung".
- closed-circuit/semi-closed circuit (also referred to as a rebreather). Here the diver breathes in from the set, and breathes back into the set, where the exhaled gas is processed to make it fit to breathe again. These existed before the open-circuit sets and are still used, but less so than open-circuit sets.
Both types of scuba provide a means of supplying air or other breathing gas, nearly always from a high pressure diving cylinder, and a harness to strap it to the diver's body. Most open-circuit scuba and some rebreathers have a demand regulator to control the supply of breathing gas. Some "semi-closed" rebreathers only have a constant-flow regulator, or occasionally a set of constant-flow regulators of various outputs.
Read more about this topic: Scuba Set
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