US Patent 7089939 Gas delivery connection assembly

An anti-asphyxia valve is adapted to, in use, be disposed between a patient and structure to deliver a breathable gas to the patient. The valve includes a housing having an interior, at least one port to provide fluid communication between the housing interior and atmosphere and at least one flap including a first portion and a second portion. The first portion is adapted for mounting to the housing. The second portion is adapted to flex between a first biased open position allowing gas to pass from the housing interior through the at least one port to atmosphere when a difference in gas pressure in the housing interior and atmosphere is below a predetermined operating threshold and a second forced closed position substantially occluding the at least one port when the difference in gas pressure between the housing interior and atmosphere is substantially equal to or above the operating threshold.