"When we exhale, a large portion of the oxygen we inhaled, around 80 percent, is exhaled..."
Adam Altman, Long Island Divers Association
Scuba diving usually involves filling a tank with air, strapping it to your back, and breathing from it underwater. This simple system is called open circuit scuba (or self-contained underwater-breathing apparatus). Before this method of scuba diving caught on, however, people were using rebreathers. In 1878, Henry Fleuss built a diving system that allowed the user to breathe the same air over and over again. Using a rubber mask, a breathing bag, a copper tank, and a bit of string, he constructed the first scuba rebreather.
A rebreather works by removing carbon dioxide from the diver's exhaled gas and recycling its usable components. The contraption uses an expandable breathing bag to hold the exhaled gas and a system of valves to keep the gas flowing in only one
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