An apparatus for supplying anesthetic agent to a fresh gas flow is disclosed herein. The apparatus includes an evaporation chamber (32) for receiving and evaporating a liquid anesthetic agent and which evaporation chamber includes an inlet opening (36) for a fresh gas for mixing evaporated anesthetic agent with the fresh gas and which evaporation chamber also includes an outlet opening (41) for conducting the gas mixture out from the evaporation chamber. The apparatus also includes an anesthetic agent sensor (43) for obtaining a signal indicative of an amount of the anesthetic agent, and a control unit (29) for receiving the signal provided by the sensor. The apparatus also includes a regulation valve (27) for regulating a flow of the liquid anesthetic agent and which regulation valve is controlled by the control unit based on at least the signal provided by the sensor. A corresponding method and arrangement is also disclosed.
