Mask vent

A mask system (220) configured to deliver air pressurized by a flow generator system by at least 4 cm H2O above atmospheric pressure to the airways of a patient to treat sleep disordered breathing (SDB) by continuous positive airway pressure (CPAP). The mask system includes an interfacing structure comprising a patient-contacting portion configured to form a seal with the patient's nose in use, two inlet conduits (232), each configured to extend from a position superior to the patient's head and along a corresponding side of the patient's head in use, and each in fluid communication with a corresponding side of the interfacing structure to deliver pressurized air to the patient's airways, and a first vent arrangement and a second vent arrangement. The first and second vent arrangements are configured to discharge gas from the mask system to atmosphere during therapy. The second vent arrangement (228) is configured to be positioned relatively distant from the patient's nose as compared to the first vent arrangement, in use, at a location superior to the patient's head, so as to direct discharged gas away from the patient and a bed partner during therapy.