Exhalation port with built-in entrainment valve

A pressure sensitive valve device for use with respiratory equipment of the type that produces a pressurized flow of breathing gas. The valve device combines the exhalation and entrainment functions in one valve with a single air path. The valve device provides an exhaust valve function during normal operation and provides a less restricted access to the ambient atmosphere in the event of respiratory equipment malfunction. The valve device includes a valve element that moves between at least two positions. During normal operation, when the pressure generating system is generating a flow of gas, the valve element is in a "closed" or "exhaust valve" position. When in the exhaust valve position, the gas flow to the atmosphere is restricted without being completely blocked off. When the flow of gas is decreased or interrupted, the valve element moves to the "entrainment valve" or "open" position that allows a greater, i.e., less restricted flow, of gas between the user and the ambient atmosphere.