The ventilation- or anesthesia device has a gas supply unit, a gas line for forming a breathing air supply system, particularly a breathing air circuit system. A gas mixing unit (1) is provided with a mixed gas tank (2). The mixed gas tank is provided with two separate outlet openings (9,10) for discharging the mixed gas from the mixed gas tank and for subsequent supply in the breathing air supply system. An independent claim is also included for a method for mixing two different gases in a ventilation- or anesthesia device.
