Review of Electronic-nose Technologies and Algorithms to Detect Hazardous Chemicals in the Environment

Novel mobile electronic-nose (e-nose) devices and algorithms capable of real-time detection of industrial and municipal pollutants, released from point-sources, recently have been developed by scientists worldwide that are useful for monitoring specific environmental-pollutant levels for enforcement and implementation of effective pollution-abatement programs. E-nose devices are ideal instruments for measuring and monitoring carbon and greenhouse-gas emissions due to their sensitivity to a wide diversity of volatile organic compounds (VOCs). A large number of e-nose instrument types, based on a wide diversity of technologies and operational mechanisms, are available to monitor gaseous and particulate pollutants released into the atmosphere, or liquid and dissolved organic pollutants released into municipal and industrial waste-water systems. Some commonly used e-nose technologies include conducting polymers (CP), metal-oxide semiconductor (MOS), quartz crystal microbalance (QCM), and surface acoustic wave (SAW) sensors. Potential pollution-detection applications of e-noses range from atmospheric pollutant (gas-leak) detection of carbon emissions from biofuel production plants and fossil-fuel production sources in the oil and gas industry to VOC-releases from numerous other industries. E-nose technologies are potentially capable of monitoring all phases of industrial manufacturing processes to minimize production of pollutants and maintain efficient, clean production lines. E-nose devices are also useful in designing more environmentallyfriendly