A demand valve is fixedly and rigidly mounted on an anesthetic gas mixer stand in close proximity to the gas mixer. A single-patient-use disposable breathing and scavenging circuit is adapted to be removably connected to the demand valve output for permitting a patient to breath gas, or a mixture gases, supplied by the gas mixer through a remotely located disposable face mask included as a portion of the breathing circuit. The breathing circuit further includes a scavenger portion for collecting exhaled waste gas from the face mask. The scavenger portion of the circuit also is disposable.
