Abstract: A detector for detecting vapors emitted from analytes includes a housing, a pump and a sensing assembly. The housing has an inlet, an outlet and an enclosed sensing volume therebetween. The pump communicates with the housing for moving a carrier sequentially through the enclosed sensing volume at a predetermined flow rate. The sensing assembly senses the vapors of the analyte delivered by the carrier as the carrier passes through the housing. The sensing assembly includes a sensing unit constructed of an amplifying fluorescent polymer, a source of excitation, a detector, and a convertor assembly.