A control system controls fresh gas dispensing for an anesthesia device, with a patient gas-measuring unit, an anesthetic-dispensing unit, a user interface, and a fresh gas regulation unit. With a transition from deactivated assistance mode to activated assistance mode, a processing unit receives a measured signal, a fresh gas signal and an assistance signal and calculates an end tidal anesthetic concentration over time based on a current volume flow, a predefined volume flow and on a current end tidal anesthetic concentration and stores this as a preset curve. A fresh gas correction signal is output upon the determined current end tidal anesthetic concentration leaving a surrounding range of the preset curve. A predefined volume flow curve is changed as a function of the correction signal. The volume flow of fed fresh gas is increased when the surrounding range is undershot and is reduced when the surrounding range is exceeded.
