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Underwater breathing apparatus can be classified as open circuit, semi-closed circuit, (including gas extenders) or closed circuit (including reclaim systems), based on whether any of the exhaled gas is recycled, and as self-contained or remotely supplied (usually surface-supplied, but also possibly from a lock-out submersible or an underwater habitat), depending on where the source of the ...
A diver with a constant workload during aerobic working conditions will use an approximately constant amount of oxygen as a fraction of the respiratory minute volume (RMV, or ). This ratio of minute ventilation and oxygen uptake is the extraction ratio K E {\displaystyle K_{E}} , and usually falls in the range of 17 to 25 with a normal value of ...
As a person breathes, the body consumes oxygen and produces carbon dioxide. Base metabolism requires about 0.25 L/min of oxygen from a breathing rate of about 6 L/min, and a fit person working hard may ventilate at a rate of 95 L/min but will only metabolise about 4 L/min of oxygen [10] The oxygen metabolised is generally about 4% to 5% of the inspired volume at normal atmospheric pressure, or ...
Aqua-Lung [1] was the first open-circuit, self-contained underwater breathing apparatus (or "scuba") to achieve worldwide popularity and commercial success. This class of equipment is now commonly referred to as a twin-hose diving regulator , [ 2 ] or demand valve .
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It is a non-profit, global organization with more than 1,300 members, which promotes scuba diving through consumer awareness programs and media campaigns such as the national Be a Diver campaign; diver retention initiatives such as DiveCaching; and an annual trade-only event for businesses in the scuba diving, action watersports and adventure ...
A diver with a RMV of 40 L/min at 50 msw (6 bar) for 10 minutes will consume 40 × 6 × 10 = 2400 litres of free air – the full capacity of a 12-litre 200 bar cylinder. Imperial examples: A diver with a SAC of 0.5 cfm (cubic feet per minute) at 100 fsw (4 ata) will consume 0.5 × 4 × 1 = 2 cfm surface equivalent.
The endurance of the cylinder can be calculated from the volume, pressure and breathing rate of the user. The formula: volume (in liters) × pressure (in bars) / 40 (litres per minute) - 10 minutes (the 10 minutes is a safety margin, or reserve), so a 6-liter cylinder, of 300 bar, is 6 × 300 / 40 - 10 = 35 minutes working duration.