Apparatus and method for detecting and identifying hazardous material in a mail stream in which hazardous particulates or material in or on mail pieces in a mail stream are detected and the mail piece bearing the hazardous material is identified. A bar code applicator applies a unique bar code to the wrapper of each mail piece identified as potentially containing hazardous material. The bar code applicator is an ink jet which applies the bar code on-the-fly. The bar code applied is encoded with specific information about the detection parameters at the time of the event in addition to specific information about the date, time of day, machine identification, temperature and humidity conditions, etc. present at the time of the event.