Abstract: A hollow disk is carried on a wheeled frame or trolley which is moved over the surface being examined. The hollow disk is slidable perpendicularly to its surface within certain limits. The disk is double walled and a certain degree of vacuum is maintained in the space between the walls during the apparatus operation.The disk wall facing the surface being examined is provided with holes and on the outer surface of the same wall a disk of para rubber is spread which is provided with the same array of holes as the hollow disk wall; the holes of the disk wall being aligned with the holes of the para rubber disk.For each sampling operation a fresh smear disk is applied on the para rubber layer which adheres thereon by the action of the dynamic vacuum existing within the hollow disk. The hollow disk is biased outwards of the frame by a calibrated spring inserted between the disk and the frame structure.