Patent ID: 8714157

Claim:
A device for delivering a supply of gases to a user comprising: a mask, in use in fluid communication with said supply of gases and supplying said gases to said user; and at least one non-closing outlet vent comprising a slot formed in said mask and at least one cover integrated with or attached to said mask and extending over said slot from a bottom edge proximate said slot to an open top edge, said cover not acting to close said at least one non-closing outlet vent and adapted to direct gases toward a mask inlet, wherein an air gap between said cover and said mask passes a substantial portion of expired gases of said user from said slot through said open top edge in an upward direction toward the top of the user's head; and wherein a separation between said mask and said cover increases between said bottom edge and said top edge of said cover in a direction of the open top edge and said bottom edge of said cover is shorter than said top edge so that said cover and said air gap are tapered outwardly in said direction of said open top edge, a cross-sectional area of said air gap transverse to a direction of air flow is larger at an outlet end of said outlet vent than an inlet end of said outlet vent adjacent said slot such that a velocity of gases passing through said air gap decreases moving toward said top edge.