An elbow assembly includes an elbow with a first portion adapted to be secured to a mask and a second portion adapted to receive pressurized gas. The first and the second portions have a connection structure allowing selective connection and disconnection between the first and second portions. The connection structure includes a pair of resilient arms provided on one of the first and second portions and a flange provided on the other of the first and second portions. Each of the arms include a claw to lock with the flange. The elbow assembly also includes an anti-asphyxia valve (AAV) assembly provided within the elbow and sandwiched between the first and second portions. The AAV assembly has a movable portion that is movable to a closed position at which the movable portion extends across a gas flow path between the first and second portions and substantially prevents a flow of gas between the first and second portions.