A scavenging system channels waste gases away from the operating room to a location outside the hospital building or a location where the gases can be discharged safely (e.g., to a nonrecirculating exhaust ventilating system). The ambient concentration of anesthetic gases in the operating room should not exceed 25 parts per million (ppm) for nitrous oxide and 2 ppm for halogenated agents. Specific anesthetic gas-scavenging systems should be used routinely. These systems consist of a collecting system, a transfer system, a receiving system, and a disposal system.