**6. Conclusion**

This chapter shows the importance of the study of gas sensors and their fundamental applications that are used in different aspects of life in addition to their importance in the dictation of toxic gases. The use of these devices can reduce the risks. To that, it is turn out the importance of classifying the materials that are used in gas sensitivity and components of gas sensors as it is explained the steps of sensitivity measurement with a description of the system used to sense the gases.
