A process for controlling the delivery of a quantity of gas to be measured through a test gas tube (60) with a pump (20), a sensor system for pressure and flow measurement (12, 14, 16) and a control and regulating unit (30). A common mode offset of a differential pressure sensor (14), determined in a calibration process, is taken into account in the process for operating the gas sampling device to increase the accuracy of a gas volume being delivered with pump (20) from the measuring environment (50).