measuring phase and the gas sensor is heated by a heating device in a desorption phase in order to accelerate desorption the heating process is continued until the temporal alteration of the measuring signal of the gas sensor falls below a threshold value application_number US 201213981799 A description fig1 shows a measurement system 10 for respired gas analysis the measurement system 10 is contained in a housing which is not shown in fig1 the measurement system 10 comprises a main circuit board 11 on which the further elements are mounted the further elements include a gas channel 12 which comprises an inlet opening 15 and an outlet opening 14 a pump unit 13 is accommodated in the gas channel 12 by means of the pump unit 13 air from outside the measurement system 10 can be drawn into the gas channel through the gas inlet 15 in this case the air passes over a nitrogen dioxide sensor 16 the nitrogen dioxide sensor 16 is a field effect transistor based gas sensor it comprises a sensitive layer 17 and a heater 18 furthermore the gas sensor 16 also comprises the typical electronic components for a field effect transistor the gas sensitive layer 17 is in this case separated as a so called suspended gate from the rest of the elements of the gas sensor 16 by a narrow air gap in this exemplary embodiment copper phthalocyanine is used as the material for the gas sensitive layer 17 the pump unit 13 the heater 18 and the electrical connections in the region of the sensitive layer 17 are connected to a control and evaluation device in the form of a microprocessor 19 the microprocessor 19 controls the pump unit so that a measurement can be carried out.