Rebreather

A rebreather is a breathing apparatus that absorbs the carbon dioxide from a diver's exhaled breath so the substantial unused oxygen it still contains can be rebreathed, in contrast to an open-circuit system that vents each exhaled breath straight into the water as bubbles. A scrubber component removes the carbon dioxide while oxygen is replenished to keep the recycled gas safe to breathe. The diving engineer Henry Fleuss designed and built the first commercially practical closed-circuit rebreather in 1878 while working for the London firm Siebe Gorman, an apparatus with a rubber mask, a breathing bag, an oxygen supply from a copper tank and carbon dioxide removal using rope yarn soaked in a caustic potash solution, good for roughly three hours of use. Beyond extending how long a diver can stay underwater on a limited gas supply, a rebreather's near-total absence of bubbles has made it especially valuable for military diving and for observing wildlife without disturbing it.