A washout vent formed of or treated with hydrophobic or hydrophilic material, or a vent coated with hydrophobic or hydrophilic material, reduces noise and/or minimizes or precludes the formation of blockage in the vent pathway due to outflow of gas from a respiratory mask. One or the other or combinations of hydrophobic and hydrophilic materials may be used to repel or wick moisture away to minimize or preclude moisture buildup on vent surfaces and/or clogging of vent pathways, particularly when using humidified air. Sintered porous plastic hydrophobic or hydrophilic materials are utilized and the porosity may be varied integrally within the vent membrane or by forming the vent from layers of materials having different porosities.
