Abstract: The invention relates to a method and means for detecting chemical contaminants on the ground. A tracked or wheeled vehicle is driven on the ground in question and a sampling screen (2) arranged as a mudflap in connection with at least one track/wheel of the vehicle is thereby contaminated by particles (3) thrown up from the ground, and an air stream carrying substances evaporated from said particles is caused to flow from said sampling screen (2) through a conduit (6) via a detection unit (4) in the vehicle. The sampling screen (2) is preferably provided with a heating device (11) to enhance the evaporation of possible chemicals from said particles.