Abstract: An absorption-type oxygen generating system is disclosed in which the nitrogen components of compressed air passing through an absorption bed is absorbed, leaving a relatively pure oxygen effluent. Regeneration of the bed is provided by depressurizing the bed and recirculating a portion of the oxygen effluent to release the nitrogen previously absorbed therein. A flow divider has two branches each providing fixed orifice therein. One branch delivers a fixed percentage of the effluent to a depressurized absorption bed for regeneration thereof. The other branch delivers the remaining effluent to a storage tank. A pressure regulating valve is provided in the second branch to maintain a constant pressure differential across the orifice of the second branch so that a constant percentage of the oxygen effluent is delivered to the storage tank regardless of the back pressure existing in such tank.