A mask system for delivering air pressurized above atmospheric pressure to the airways of a patient to treat sleep disordered breathing (SDB) by continuous positive airway pressure (CPAP) may include a mask having a cushion configured to form a seal with the patient's nose; two inlet conduits, each of the two inlet conduits configured to extend from a position superior to the patient's head and along a corresponding side of the patient's head, and each of the two inlet conduits being in fluid communication with a corresponding side of the mask to deliver pressurized air to the mask; a first vent arrangement configured to be positioned superior to the patient's head in use and configured to discharge gas to atmosphere during therapy; and a second vent arrangement configured to be positioned inferior to the first vent arrangement in use and configured to discharge gas to atmosphere during therapy.