Scuba, or the acronym SCUBA, describes a diver's Self-Contained Underwater Breathing Apparatus. According to the diving experts reporting for California's MarineBio Conservation Society, the modern scuba systems developed out of the ancient desire to know the underwater world as well as the world of land and sky. Underwater breathing with a snorkel or an air pump did not become self contained until the 19th Century.
First Scuba
Between 500 B.C., when a Greek sailor sabotaged the Persian war fleet from underwater, using a hollow reed snorkel, and 1825, divers needed surface air. But in 1825, William James an English inventor, developed an "air girdle," an pressurized air reservoir tank that encircled a diver's chest allowing small gulps of air until the tank was empty. This was the first primitive scuba equipment. Forty years later, French inventors Auguste Denayrouse and Benoit Rouquayrol built and patented their "Aerophore," a pressurized, steel air tank worn on the back with a mouthpiece to deliver air through a pressure-sensitive demand regulator. The tank held enough air for brief, independent activities but needed frequent refilling from the surface.
Oxygen, Carbon Dioxide And The Bends
In 1667, Robert Boyle, an English physicist, discoverer of Boyle's gas laws, submerged animals in pressurized chambers. On raising the creatures back to the lower surface-air pressure, he observed convulsions due to decompression -- "the bends." In 1876 the English merchant seaman, Henry A. Fleuss, filled pressurized canisters with pure oxygen. This eliminated the bends, later recognized as bubbles in the bloodstream from nitrogen dissolved from pressurized air. But pure oxygen under pressure is toxic. And breathing in and out of an oxygen tank accumulated CO2. Fleuss passed the diver's exhaled air through caustic potash to remove CO2 and limited diving to shallower, low-pressure activities. Under these conditions he gained up to three hours of productive underwater work time, eliminated the bends and minimized oxygen toxicity with his improved scuba system.
Safer Dives
Toxicity of pure oxygen, as in Fleuss's scuba system, increases -- and the safe duration of use decreases -- with higher pressures at greater depths, according to Dr. Laurence Martin, author of the 1997 book "Scuba Diving Explained." Modern research solves the problems of oxygen toxicity and the bends by replacing the nitrogen in air with helium. Scuba divers now select from among various gas mixtures for the one best suited to their needs and allowing deeper dives.
Jacques Cousteau
Jacques Cousteau, famed oceanographer and explorer, combined the improvements in scuba equipment, added his own refinements, especially an improved pressure regulator for better breathing control, to outfit his expeditions. By 1952, Cousteau's advanced scuba system, the "Aqua Lung," was marketed in France, Canada, Great Britain and the U.S. In the 21st century, diving certificates call for knowledge of equipment technology and underwater gas physics, according to scuba trainers at The Scuba Guide in Ontario, Canada. Nearly 1,000,000 new certifications of scuba diving competency are earned by divers every year worldwide.
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