An anesthetic evaporator with a pressure control circuit has a differential pressure pick-up (18) can be calibrated in a simple manner. A switchover device (20) is provided according to the present invention at a bypass gap (3), which is designed to connect the gas inlet (4) directly with the gas outlet (5) via a first bypass line (23) and to bridge over the bypass gap (3) via a second bypass line (26) connected to a ventilation duct (27) in a first switching position. The gas flow from the gas inlet (4) to the gas outlet (5) is established via the bypass line (2) in a second switching position. The calibration of the differential pressure pick-up (18) with the pneumatic connections (16, 17) is performed in the first switching position of the switchover means (20) via the ventilation duct (27), which is open toward the ambient atmosphere.