Scuba diving / Malvan trip memories / ocean life / marine life
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- Опубліковано 9 вер 2024
- Scuba diving is a mode of underwater diving whereby divers use breathing equipment that is completely independent of a surface breathing gas supply, and therefore has a limited but variable endurance.[1] The name scuba is an anacronym for "Self-Contained Underwater Breathing Apparatus" and was coined by Christian J. Lambertsen in a patent submitted in 1952. Scuba divers carry their own source of breathing gas, usually compressed air,[2] affording them greater independence and movement than surface-supplied divers, and more time underwater than free divers.[1] Although the use of compressed air is common, a gas blend with a higher oxygen content, known as enriched air or nitrox, has become popular due to the reduced nitrogen intake during long or repetitive dives. Also, breathing gas diluted with helium may be used to reduce the effects of nitrogen narcosis during deeper dives.
Two basic functional variations of scuba are in general use: open-circuit-demand, and rebreather. In open-circuit demand scuba, the diver expels exhaled breathing gas to the environment, and each breath is delivered at ambient pressure, on demand, by a diving regulator, which reduces the pressure from the storage cylinder. The breathing gas is supplied through a demand valve; when the diver inhales, they reduce the pressure in the demand valve housing, thus drawing in fresh gas. In rebreather scuba, the system 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 the design.
Within these systems, various mounting configurations may be used to carry the scuba set, depending on application and preference. These include: back mount, which is generally used for recreational scuba and for bailout sets for surface supplied diving; side-mount, which is popular for tight cave penetrations; sling mount, used for stage-drop sets; decompression gas and bailout sets where the main gas supply is back-mounted; and various non-standard carry systems for special circumstances.
The most immediate risk associated with scuba diving is drowning due to a failure of the breathing gas supply. This may be managed by diligent monitoring of remaining gas, adequate planning and provision of an emergency gas supply carried by the diver in a bailout cylinder or supplied by the diver's buddy, and the skills required to manage the gas sources during the emergency.
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