A conduit for delivering a supply of gas under a positive pressure includes a conduit wall having a first conduit end and a second conduit end. The first conduit end is adapted to be attached to the supply of gas. The conduit wall is deformable between (a) an open condition in which the conduit wall defines a conduit passage along which the supply of gas can travel between the first conduit end to the second conduit end, and (b) a collapsed condition in which the conduit wall substantially collapses the conduit passage.