Inert gases find wide applications in industry as insulating gas medium in high voltage switch gears, as refrigerant gas in cooling plants and air conditioning systems etc. However most of these gases are greenhouse gases and cause ozone depletion and global warming. Hence release of these gases into atmosphere even in very small quantity need to be monitored strictly. MEMS gas sensors are capable of detecting gas traces to the level of ppt (parts per trillion). The most commonly used MEMS topology for gas sensing is based on metal oxide thin films along with micro heaters. However this topology is not suitable for inert gases because they do not react with the metal oxide to change the conductivity of the thin film. Hence we need to design different topologies like Surface Acoustic Wave (SAW) or Cantilever based architecture both of which respond to the mass loading effect which is useful to detect inert gases. In this work we have designed both SAW and Cantilever based MEMS Sensors to detect inert gas using nanomaterials like Carbon Nanotubes and the topologies are simulated using COMSOL Multiphysics Software. Both the topologies are found to be suitable for detecting inert gases.