Abstract: The ever increasing applications of sensor networks is causing a growth in demand for low cost, energy efficient sensors for monitoring physical environment such as temperature, gas concentration or pressure, especially in hot-process areas. The paper presents a 3D model of a Surface Acoustic Wave Gas sensor for detection of CO2 in high temperature areas. A robust and sensitive chemisensor has been realized by using the SAW phenomenon. In this study, nanostructures have been added in addition to the metallic layer to increase the surface to volume ratio of the sensor. The sensitivity of the sensor has been increased by using a piezoelectric material as a sensing layer. The choice of material absorption has been chosen by using Hard-Soft-Acid –Base theory, which is a relatively new concept to determine polymers for the active layer. The reliance of SAW reflection factor for unidirectional IDTs loaded by impedance on its resistive value was investigated, The sensor showed great results when exposed to varied concentrations of CO2 . Study also showed that langasite showed a stable frequency at higher temperature as compared to commonly used litium niobate. The design and simulation of the sensor is done using the Finite Element Analysis (FEA) module of COMSOL Multiphysics. The high temperature stability, fast response and robustness of the sensor showed promising industry applications.