A system comprising a respiratory mask for delivering a supply of breathable gas to the entrance of a patient’s airways for amelioration or treatment of a respiratory disorder, the respiratory mask having venting apparatus configured to vent a plenum chamber of the respiratory mask to ambient, the venting apparatus comprising: a first adjustable vent； a second adjustable vent； and actuator apparatus on the mask to (1) automatically vary the first adjustable vent in response to a first control system signal for adjusting the first adjustable vent, and (2) to automatically vary the second adjustable vent in response to a second control system signal for adjusting the second adjustable vent； the system further comprising: a controller adapted to couple with the actuator apparatus and generate the first control system signal and the second control system signal, and wherein each of the first adjustable vent and the second adjustable vent is controllable by the controller, wherein the controller is configured to control an operation of the actuator apparatus so as to alter an amount of flow of the breathable gas exiting each vent, and wherein the operation adjusts the first adjustable vent distinctly from the second adjustable vent by coordinating (a) an increase in an amount of a flow of the breathable gas exiting one of the first adjustable vent and the second adjustable vent, with (b) a decrease in an amount of flow of the breathable gas exiting the other one of the first adjustable vent and the second adjustable vent.
