An apparatus for providing a concentrated product gas, comprising: an input device for selecting a first desired output flow rate setting for the concentrated product gas; a product gas source for providing the concentrated product gas for dispensing; a pressure sensor for monitoring a pressure of the concentrated product gas; a conserver valve comprising an output connection associated with a user, a vent connection associated with a vent port, and a gas connection associated with the concentrated product gas, wherein the output connection is adapted to switch from the vent connection to the gas connection and vice versa; a flow sensor monitoring a flow indicative of a breathing cycle for the user; and a controller in operative communication with the input device and pressure sensor and adapted to selectively switch the conserver valve to selectively dispense a bolus of concentrated product gas based at least in part on the selected output flow rate setting and monitored pressure; wherein the controller is in operative communication with the flow sensor, is adapted to determine a breathing characteristic of the user based at least in part on the monitored flow, and is adapted to selectively switch the conserver valve based at least in part on the determined breathing characteristic; wherein the controller is adapted to determine a start time for dispensing the bolus of concentrated product gas to the user via the output connection based at least in part on a relation between the determined breathing characteristic and a trigger threshold indicative of inhalation; wherein the controller is adapted to determine a pressure summation threshold based at least in part on the selected output flow rate setting; and wherein the controller is adapted to determine a time duration for dispensing the bolus of concentrated product gas based at least in part on a relation between the monitored pressure and the pressure summation threshold. an input device for selecting a first desired output flow rate setting for the concentrated product gas; a product gas source for providing the concentrated product gas for dispensing; a pressure sensor for monitoring a pressure of the concentrated product gas; a conserver valve comprising an output connection associated with a user, a vent connection associated with a vent port, and a gas connection associated with the concentrated product gas, wherein the output connection is adapted to switch from the vent connection to the gas connection and vice versa; a flow sensor monitoring a flow indicative of a breathing cycle for the user; and a controller in operative communication with the input device and pressure sensor and adapted to selectively switch the conserver valve to selectively dispense a bolus of concentrated product gas based at least in part on the selected output flow rate setting and monitored pressure; wherein the controller is in operative communication with the flow sensor, is adapted to determine a breathing characteristic of the user based at least in part on the monitored flow, and is adapted to selectively switch the conserver valve based at least in part on the determined breathing characteristic; wherein the controller is adapted to determine a start time for dispensing the bolus of concentrated product gas to the user via the output connection based at least in part on a relation between the determined breathing characteristic and a trigger threshold indicative of inhalation; wherein the controller is adapted to determine a pressure summation threshold based at least in part on the selected output flow rate setting; and wherein the controller is adapted to determine a time duration for dispensing the bolus of concentrated product gas based at least in part on a relation between the monitored pressure and the pressure summation threshold.