A compact scanning apparatus has an infrared laser adapted to emit light. The light is delivered as a beam by an optical system to illuminate an interrogation area on the surface of an object being scanned. Such illumination has sufficient intensity and duration to cause selective desorption of molecules of the contraband substance, which are present on the surface, without substantially damaging the surface. A collection system collects at least a portion of the desorbed molecules. At least a portion of the collected molecules is thermally decomposed to form NO₂ and transferred to a reaction cell containing an aqueous, alkaline, luminol-containing solution. The NO₂ reacts with the luminol to produce light by chemiluminescence. A light detector registers the presence of this light as indicative of the detection of the contraband substance, and activates a signaling device to provide an audible or visible alarm. The apparatus rapidly detects the presence of a wide variety of contraband substances in an accurate, reliable manner. It provides for automated screening, with the result that vagaries of human performance are virtually eliminated. False alarms are reduced and detection efficacy is increased. A traceable residue of the detected contraband is left on the article for use in forensic analysis.