Gas Sensing Techniques in Electronic Nose and its Applications: A Review

Electronic noses instruments were developed as systems for the discrimination of gases and odors. An electronic nose is a portable device which strives to sniff complex mixtures of volatile organic compounds. It consists of a large array of chemical sensors with associated signal conditioning and pattern recognition techniques. An electronic noses employs different types of gas sensors that uses a sensor array which results in partially overlapping sensitivity such that each sensor responds to a range of gases rather than to a specific one. Signals resulting from these arrays require to be examined by pattern recognition techniques such as artificial neural networks (ANNs). The gas sensing methods referred to the different types of sensors are mainly used for swift detection of gases in application. Each one of these sensors has its own kind of response in the sensor array. The electronic noses sensors are employed for the identification of gases/odors, such as volatile organic compounds (VOCs) to solve a broad variety of problems in food and beverages industry, chemical and biological hazards, wide area monitoring, environmental monitoring, process monitoring, flavors, fragrances, cosmetics productions, safety, security and military use. In this research paper, we study the operating principle of electronic nose technology, gas sensing sensor techniques and explain a range of applications of electronic noses in extensive areas.