A respirator or anesthesia apparatus, for the artificial respiration of a patient, has a gas delivery device, at least one gas line for forming a breathing air line system, at least one gas mixing means with a mixed gas tank and at least two inlet openings with a shut-off member each for separately feeding at least two different gases to be mixed into the mixed gas tank and for subsequently feeding the mixed gas into the breathing air line system. The mixed gas tank is provided with at least two separate outlet openings for releasing the mixed gas from the mixed gas tank and for subsequently feeding it into the breathing air line system.
