page_title: Scuba set
section_title: Harness configuration
hierarchical_section_title: Scuba set / Harness configuration
caption_attribution_description: English: A SCUBA diver about to enter the sea from an RIB.
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: The scuba set can be carried by the diver in several ways. The two most common basic mounting configurations are back-mount and side-mount, and back-mount may be expanded to include auxiliary side-mounting, including bungee-constrained low profile side-mount, and the less compact sling-mount or stage-mount arrangement.
  Most common for recreational diving is the stabilizer jacket harness, in which a single cylinder, or occasionally twins, is strapped to the jacket style buoyancy compensator which is used as the harness. Some jacket style harnesses allow a bailout or decompression cylinder to be sling mounted from D-rings on the harness. A bailout cylinder can also be strapped to the side of the main back-mounted cylinder.
  Another popular configuration is the backplate and wing arrangement, which uses a back inflation buoyancy compensator bladder sandwiched between a rigid backplate and the main gas cylinder or cylinders. This arrangement is particularly popular with twin or double cylinder sets, and can be used to carry larger sets of three or four cylinders and most rebreathers. Additional cylinders for decompression can be sling mounted at the diver's sides.
  It is also possible to use a plain backpack harness to support the set, either with a horse-collar buoyancy compensator, or without any buoyancy compensator. This was the standard arrangement before the introduction of the buoyancy compensator, and is still used by some recreational and professional divers when it suits the diving operation.
  Surface-supplied divers are generally required to carry an emergency gas supply, also known as a bailout set, which is usually back-mounted open circuit scuba connected into the breathing gas supply system by connecting an interstage hose to the gas switching block, (or bailout block), mounted on the side of the helmet or full-face mask, or on the diver's harness where it can easily be reached, but is unlikely to be accidentally opened. Other mounting arrangements may be used for special circumstances.
  Side-mount harnesses support the cylinders by clipping them to D-rings at chest and hip on either or both sides, and the cylinders hang roughly parallel to the diver's torso when underwater. The harness usually includes a buoyancy compensator bladder. It is possible for a skilled diver to carry up to 3 cylinders on each side with this system.
  An unusual configuration which does not appear to have become popular is the integrated harness and storage container. These units comprise a bag which contains the buoyancy bladder and the cylinder, with a harness and regulator components which are stored in the bag and unfolded to the working position when the bag is unzipped. Some military rebreathers such as the Interspiro DCSC also store the breathing hoses inside the housing when not in use.
  Technical divers may need to carry several different gas mixtures. These are intended to be used at different stages of the planned dive profile, and for safety reasons it is necessary for the diver to be able to check which gas is in use at any given depth and time, and to open and close the supply valves when required, so the gases are generally carried in fully self-contained independent scuba sets, which are suspended from the harness at the diver's sides. This arrangement is known as stage mounting. Stage sets may be cached along a penetration guideline to be retrieved during exit for convenience. These are also sometimes called drop tanks.
caption: Backplate and wing harness
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