Editing Scuba set (section)

===Semi-closed rebreather===
A semi-closed circuit rebreather may have an endurance of about 3 to 10 times that of the equivalent open-circuit dive, and is less affected by depth; gas is recycled but fresh gas must be constantly injected to replace at least the oxygen used, and any excess gas from this must be vented. Although it uses gas more economically, the weight of the rebreather encourages the diver to carry smaller cylinders. Still, most semi-closed systems allow at least twice the duration of average sized open-circuit systems (around two hours) and are often limited by scrubber endurance.{{citation needed|date=December 2016}}