page_title: Scuba set
section_title: Rebreathers
hierarchical_section_title: Scuba set / Types / Rebreathers
caption_attribution_description: English: rebreather inspiration front
context_page_description: A scuba set is any breathing apparatus that is carried entirely by an underwater diver and provides the diver with breathing gas at the ambient pressure. Scuba is an anacronym for self-contained underwater breathing apparatus. Although strictly speaking the scuba set is only the diving equipment which is required for providing breathing gas to the diver, general usage includes the harness by which it is carried, and those accessories which are integral parts of the harness and breathing apparatus assembly, such as a jacket or wing style buoyancy compensator and instruments mounted in a combined housing with the pressure gauge, and in the looser sense it has been used to refer to any diving equipment used by the scuba diver, though this would more commonly and accurately be termed scuba equipment or scuba gear. Scuba is overwhelmingly the most common underwater breathing system used by recreational divers and is also used in professional diving when it provides advantages, usually of mobility and range, over surface supplied diving systems, and is allowed by the relevant code of practice.
  Two basic functional systems of scuba are in general use: open-circuit-demand, and rebreather.
context_section_description: A rebreather recirculates the breathing gas already used by the diver after replacing oxygen used by the diver and removing the carbon dioxide metabolic product. Rebreather diving is used by recreational, military and scientific divers where it can have advantages over open-circuit scuba. Since 80% or more of the oxygen remains in normal exhaled gas, and is thus wasted, rebreathers use gas very economically, making longer dives possible and special mixes cheaper to use at the cost of more complicated technology and more possible failure points. More stringent and specific training and greater experience is required to compensate for the higher risk involved. The rebreather's economic use of gas, typically 1.6 litres (0.06 cu ft) of oxygen per minute, allows dives of much longer duration for an equivalent gas supply than is possible with open-circuit equipment where gas consumption may be ten times higher.
  There are two main variants of rebreather – semi-closed circuit rebreathers, and fully closed circuit rebreathers, which include the subvariant of oxygen rebreathers. Oxygen rebreathers have a maximum safe operating depth of around 6 metres (20 ft), but several types of fully closed circuit rebreathers, when using a helium-based diluent, can be used deeper than 100 metres (330 ft). The main limiting factors on rebreathers are the duration of the carbon dioxide scrubber, which is generally at least 3 hours, increased work of breathing at depth, reliability of gas mixture control, and the requirement to be able to safely bail out at any point of the dive.
  Rebreathers are generally used for scuba applications, but are also occasionally used for bailout systems for surface supplied diving.
  The possible endurance of a rebreather dive is longer than an open-circuit dive, for similar weight and bulk of the set, if the set is bigger than the practical lower limit for rebreather size, and a rebreather can be more economical when used with expensive gas mixes such as heliox and trimix, but this may require a lot of diving before the break-even point is reached, due to the high initial and running costs of most rebreathers, and this point will be reached sooner for deep dives where the gas saving is more pronounced.
caption: An Inspiration rebreather seen from the front
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