Abstract: A system utilizing the central vacuum system in the dental operatory to exhaust analgesic or anesthetic gas from a gas administration assembly. The system includes a nosepiece fitting over the nose of a patient, an exhaust assembly for removing exhaled gas from the nosepiece, and an exhaust chamber formed around the periphery of the nosepiece for scavenging gas leaking through the facial seal at the rim of the nosepiece.

Abstract: A scavenging mask apparatus for administering gas to a patient, the apparatus comprising a nasal cannula for delivering gas to the patient's nostrils, a tube connecting the cannula to a source of gas, a nosepiece adapted to fit over the nose and cannula, and a tube connecting the nosepiece to a source of vacuum. Gas exhaled through the patient's nostrils or escaping from the cannula is scavenged by the air flow in the nosepiece, thereby minimizing loss of gas to the environment. The nosepiece is also provided with a plurality of holes in the underside thereof to scavenge gas exhaled through the patient's mouth.