The detection of gas molecule is important for environmental monitoring, safety, health issues, chemical processing control, agriculture and medical applications. This is much important for mine workers. Recently metal oxide gas sensors by nanostructures have stirred interest and have found their way in many applications due to their high sensitivity, material design compliances and high safety properties. It is indicated that nanoparticles formation on the film surfaces, grain sizes, gas types and operating temperatures have a severe effect on the chemisorption and physisorption process.