The AC4 module records the individual exhaust air volumes of all the exhaust fans in the laboratory and calculates a total air volume from them. A distinction is made between different operating states (e.g. daytime operation, nighttime operation), for which a corresponding minimum air exchange is maintained. On this basis, the air volumes of the individual consumers can be individually controlled according to their needs. In the event of deviations from the target values, an automatic alarm is issued. Thanks to optimal (minimum) ventilation, the required total air volumes can be reduced at any time, thereby achieving the highest possible energy efficiency.