Abstract: A pneumatically amplified conservation valve controls a flow of gas, such as oxygen, to a hospital patient. A sense tube monitors pressure variations as a result of exhalation by the user. The exhalation pressure variation deflects a diaphragm which closes a check valve that serves to vent gas through a bleed port. When the check valve closes the bleed gas is restricted in a chamber which deflects the diaphragm which in turn drives a connector that pushes a plunger to close a port that is connected to the source of gas through a supply tube. The gas is normally supplied through the supply tube and a normally open pneumatic valve to an output tube and then to the user. The pneumatically amplified conservation valve provides gas to the user except when the user is exhaling thereby substantially saving the amount of gas that must be provided to a user.