A CPAP system is described for improved respiratory therapy of patients. In particular a patient interface is disclosed with an outlet vent with lower noise levels and more diffused outlet flow over prior art outlet vents. The outlet vent includes a main vent which is diffused and muffled and a higher resistance vent provided in case the main vent is blocked. The outlet vent is removable for easy maintenance and provides indication to the user when maintenance is required. The outlet vent described may be used on nasal masks, mouthpieces and patient interfaces generally. <；IMAGE>；
