WAKEFIELD, Mass., Dec. 5 -- Implant Sciences Corp. said it has developed a system that can detect vapor from at least five types of explosives at airborne concentrations measured in parts per trillion. The system is 100 to 1000 times more sensitive than the capabilities of explosives-sniffing dogs, the company said. It has been in research and development for over two years, can be portable and battery powered and is capable of detecting the presence of explosives from their natural vapor. This avoids having to harvest actual explosive particles and physically place them inside the machine, as must be done with some other existing equipment. A portable, battery-powered prototype can selectively identify a wide range of explosives within one second, sound an alarm and display and print out the concentrations in parts per trillion. The design of the system relies on the laser-resonant enhanced multiphoton ionization phenomenon (REMPI) previously used for isotope enrichment. The REMPI ion source is integrated with an ion mobility spectrometer, an instrument used in explosives and narcotics detection. The system is undergoing qualification testing in anticipation of approval by certain US and foreign government agencies responsible for explosives or contraband detection.