Abstract: An emission detector for detecting explosives or illegal drugs is disclosed. The emission detector is portable, non-invasive, and easily hidden. The emission detector includes an illumination module, including a light source for outputting a flash of ultraviolet light having a wavelength of from 190 nm to 350 nm, the output flash illuminating an out-gassing material; and a detector module, optically aligned with the illumination module, the detector module including a molecular filter that is optically matched to the ground state absorption of ambient gas molecules, the molecular filter having an output, and a photomultiplier optically coupled to the output of the molecular filter for detecting a secondary fluorescent signature from the out-gassing material. The out-gassing material can be an explosive or an illegal drug. The ambient gas molecules can be at least one of NO, CH, OH, CHO, CH2O, C2H or NO2.