Air quality is closely related to the concentration of pollutant gases (NO2, SO2, CO, O3, etc.) in the environment. Excessive pollutant gases can adversely affect both the environment and human health, so efficient gas detection is crucial for human health and supporting air quality sustainability. Conventional gas detection methods generally suffer from various shortcomings, such as susceptibility to environmental factors, high operating temperatures, and low selectivity, hindering the further development of gas detection technology. With the emergence of nanotechnology, the construction of nano gas sensors is considered a promising solution to address the limitations of conventional detection techniques. The research on nano gas sensors focuses on the design and synthesis of nanomaterials, which are expected to exhibit superior gas detection capabilities owing to their distinctive structural characteristics and enhanced surface reactivity at the nanoscale. In general, the involvement of nanomaterials in gas detection includes nanosorbents for the sampling process and nano-gas-sensing materials for the sensing process. In this chapter, we briefly introduce the hazards and sources of environmental pollutant gases, summarize the nanosorbents and nano-sensing materials used for gas detection, and the synthesis methods of nanomaterials.