A device is provided for testing surfaces of a card for the presence of explosives, drugs or other substances of interest. The device includes a slot for receiving the card. Thin metallic wiper blades are dispose in alignment with the slot and wipe over surfaces of the card as the card is passed through the slot. Thus, substances on the surface of the card are transferred to the wiper blade. The wiper blade then is enclosed and rapidly heated to desorb the material retrieved from the card. The enclosure then is placed in communication with a detector to test for the presence of substances of interest.