Vent system for CPAP patient interface used in treatment of sleep disordered breathing

A patient interface for delivery of a flow of pressurized, breathable gas generated by a flow generator at a treatment pressure that is continuously positive with respect to ambient air pressure, while a patient is sleeping, to an entrance to the patient's airways to ameliorate sleep disordered breathing, said patient interface comprising:

• a patient contacting portion configured to seal against an area surrounding the patient's nostrils to deliver the flow of pressurized, breathable gas to the patient's airways;
• a cavity bounded at least partly by the patient contacting portion, the cavity configured to be pressurized at the treatment pressure by the flow of pressurized, breathable gas;
• a swivel elbow configured to be connected to an air delivery conduit to receive the flow of pressurized, breathable gas generated by the flow generator;
• and
• a vent assembly comprising:
• a first vent having a plurality of first holes configured to allow a first flow of gas to pass through the plurality of first holes;
• and a second vent having at least one second hole configured to allow a second flow of gas to pass through the at least one second hole,
• wherein the first vent has a first vent characteristic and the second vent has a second vent characteristic that is different from the first vent characteristic, and
• wherein the vent assembly is configured to allow the first flow of gas to exit through the plurality of first holes to atmosphere and to allow the second flow of gas to exit through the at least one second hole to atmosphere, the first flow of gas and the second flow of gas exiting from the vent assembly to atmosphere simultaneously.