Method and device for identifying gases and/or ion mobility spectrometer and method for offsetting residual humidity are provided. The object of the invention is to develop a generic method for offsetting residual humidity in an ion mobility spectrometer and a related device, which has a simple structure and which fully exploits the reduced diffusion. This is achieved by a variable drift chamber drift gas velocity, which leads to differing penetration depths of the humidity into the drift chamber, and thus to variable residual humidities in the drift chamber. Methods of this type and the associated devices for detecting and identifying gases are used to recognise and identify chemical compounds, in particular explosive materials or material compounds and/or those which are damaging to health, and which must be identified in very low concentrations.