Silicon-On-Insulator (SOI) technologies are an ideal solution that can be used in harsh environments because they can cope with more extreme conditions. These specialized sensors can be used in applications such as domestic and other small-scale boilers, CO2Capture and Sequestration, oil & gas storage and transportation, and automotive. SOI is the most advanced CMOS Technology available today and its various features make it a very attractive platform for several applications. There are several advantages and very special features of SOI technology for sensing applications requiring temperatures in excess of the typical bulk silicon junction temperatures of 150oC. The structures used in SOI sensors are micro-hotplate, micro-wire, thermo-diodes etc. And finally the study of the concepts, structures and prototypes of simple and smart micro-hotplate and Infra Red (IR) based emitters for NDIR (Non Dispersive IR) gas sensors that are used in harsh environments.