What is "scuba set"

n. The set of equipment required by a scuba diver to be at ease when submerged for extended periods of time. Modern equipment sets include tanks containing mixes of nitrogen in varied ratios with oxygen, a buoyancy control device, a first- and second-stage regulator (to allow the regulated flow of gas from the tank into the user's respiratory system), a wetsuit and accessories for heat insulation, fins for underwater propulsion, a mask (to see underwater)(,) and a snorkel (for moving around the surface of the water without using up breathing gas). Many divers also choose to dive with a diving knife (in case of a tangle with a net, etc.), and night divers may also dive with a waterproof flashlight.

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. Scuba is overwhelmingly the most common underwater breathing system used by recreational divers. A scuba set is also used in professional diving when it provides advantages, usually of mobility and range, over surface supplied diving systems.

Two basic configurations of scuba are in general use:

• Open-circuit-demand scuba expels exhaled air to the environment, and requires each breath be delivered to the diver on demand by a diving regulator, which reduces the pressure from the storage cylinder and supplies it through the demand valve when the diver reduces the pressure in the demand valve slightly during inhalation.
• Rebreather scuba recycles the exhaled gas, removes carbon dioxide, and compensates for the used oxygen before the diver is supplied with gas from the breathing circuit. The amount of gas lost from the circuit during each breathing cycle depends on the design of the rebreather and depth change during the breathing cycle. Gas in the breathing circuit is at ambient pressure, and stored gas is provided through regulators or injectors, depending on design.