Abstract: This disclosure pertains to a gas scavenger apparatus utilized to recover anesthesia-logical gases derived during surgical procedures and to dispose same to a closed vacuum line substantially limiting the inadvertant escapage into the atmosphere. A reservoir bag is connected to the patient's anesthetic circuit, which in turn is connected to a scavenger valve. The vacuum line constantly empties the reservoir bag drawing off the waste gas accumulated therein. When the reservoir bag is substantially empty, a valve admits ambient air, as well as waste gas, into a chamber emptied by the vacuum line. Thus, the vacuum line does not act on the patient's anesthetic circuit, serving only to empty the reservoir bag as waste gas accumulates therein.