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Scuba Diving

 

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Overview
Scuba-from the phrase "self-contained underwater breathing apparatus"-refers to a type of diving in which an individual carries his or her own supply of air. This air supply is stored within a steel or aluminum cylinder called a scuba tank. A device called a regulator "taps" the pressurized air and adjusts its flow for breathing. Prior to the dive, a mechanical compressor fills the tank with a large volume of air. The pressure produced by this compressed air can exceed 200 times the standard atmospheric pressure! As a diver breathes, flow-adjusting devices called stages drop the flow pressure. Air that is exhaled does not return to the scuba tank. Instead, it is released and observed as the rush of rising bubbles. Sport divers can safely dive to a depth of about 39 meters (130 feet) or five atmospheres of pressure. Although the first crude scuba apparatus was invented over 150 years ago, it was Jacques-Yves Cousteau and Emile Gagnan who perfected the modern day Aqua-Lung. Unlike the "hard-hat" divers that relied on a surface air hose, Cousteau (in the early 1940s) had attained untethered freedom.

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