A method for attaching a removable, washout vent insert to a CPAP mask, the CPAP mask comprised of a rigid plastics shell having an inlet tube, the rigid plastics shell having an opening bounded by a rim, the vent insert being made of a material more flexible than the rigid plastic shell, the vent insert having a plurality of orifices, the vent insert, in a cross-sectional view, having a recess located at its periphery, includes: squeezing the vent insert along its longitudinal axis; aligning the vent insert so it is oriented to match the shape of the opening; inserting the vent insert into the opening; and releasing the vent insert once it is within the opening, the vent insert resiliently expanding to engage the rim of the opening.