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 .