Abstract: A divers two-stage gas reclaim back pressure regulator is described having mutually concentric side-by-side annular first and second chambers interconnected by a central tubular duct one end of which is cooperable with a first stage diaphragm to form a first stage valve. A third chamber for connection to a gas reclaim line is disposed between the first and second stages and communicates with the latter by way of a plurality of radially-increasing-in-size openings through an annular land of convex configuration on which a second diaphragm seats. A biasing compession spring for the second stage is located in the mentioned tubular duct. An auxiliary closure is provided by a valve element carried on the second diaphragm and capable of seating on the second stage end of the duct. The arrangement is compact, demands relatively low exhalation operation pressure and is tolerant of intruding foreign matter.