Topic summary
Automatic diluent valve
Extracted from the Wikipedia article Diving rebreather.
Automatic diluent valve (ADV)
This has a similar function to an open circuit demand valve., and in many cases uses the mechanism from a commonly available open circuit demand valve. It adds gas to the circuit if the volume in the circuit is too low. The mechanism is either operated by a dedicated diaphragm like in a scuba second stage, or may be operated by the top of a bellows type counterlung reaching the bottom of its travel.