The method and device for gas analysis, in partic. for medical use, enable determination of the instantaneous partial press. or the concentration of a component of a gas mixture using a mass spectrometer based on the quadrupole system. The method enables measurements to be made rapidly in sequence as required when the component partial press. varies with time. A press. is generated in the ion source which is higher than the measurable operating press. in the other spectrometer sections. The gas components are selected by a control signal consisting of the sum of a signal associated with a single component and a time varying signal. The signal controls the gas analyser detector.
