The validation of a qualitative ion mobility spectrometry (IMS) procedure for the detection of trace amounts of heroin and cocaine on incriminated material using a vacuum cleaner for sampling is presented. The limit of detection, the limit of decision, selectivity and robustness were determined. As an approach, robustness was determined using ionizational interferences and matrix effects. By using this simple sampling procedure, a positive result for incriminated clothes needs a contamination of 250ng cocaine and 1000ng heroin, respectively.