Abstract: “Over the last decade, there have been major advances in the area of “e-sensing”, in both, technical and commercial aspects. An e-nose is a device that mimics human olfactory system. It perceives odor/flavor and characterizes each odor with a unique signal pattern. E-nose comprises of sensor block followed by an analysis block which performs feature extraction and pattern recognition. This paper reviews different types of gas sensors employed in electronic noses till date. It describes the operating principles of major sensor types and their applications. It lists the various advantages and disadvantages of all the mentioned types that are used in e-nose”

Keywords: Electronic nose (e-nose), Quartz crystal microbalance (QCM), conducting polymers, Surface acoustic waves (SAW), metal oxide semiconductor field effect transistor (MOSFET), optical sensors