A respiratory face mask is provided suitably sized and configured to engage at least the nose portion and mouth portion of a patient's face. Gas from a gas supply and scavenging set normally used in dentistry is operatively coupled to the mask via a breathing circuit to supply fresh gas and evacuate exhaled waste gas. In an alternatively preferred embodiment, the fresh gas supply tube and the exhalation limb of the breathing circuit are replaced by a single length of co-axial flexible tubing connected between the face mask and a branched coupling. The branched coupling, in turn, includes a first branch for connection to the fresh gas supply nozzle of the "dental" set-up and a second branch for connection to a flexible flow-through reservoir bag used to store waste or exhaled gas. A one-way valve is disposed between the second branch output nozzle and the input of the flexible bag. The output of the flexible flow-through bag is connected to the vacuum module of the "dental" set-up. The second branch of the coupling, the one¬ way valve, and the flexible flow-through reservoir bag define the exhalation limb of the breathing circuit.
