Overview: With the development of economy, human demands for chemical materials are increasing. Although these chemical materials provide great convenience and improvement to our daily lives, gas leakage accidents in various fields happen frequently. Leakage of the commonly used flammable and explosive gases such as liquefied petroleum gas, methane and vinyl chloride may cause explosions or fires. Gas leakage accidents not only cause huge economic losses, but also can cause casualties. In addition, some non-toxic, odorless and seemingly harmless gases can also cause great harm to the environment. For example, SF6 gas, which is commonly used in power systems, and gases such as CO2 emitted in production will cause the greenhouse effect, resulting global warming. Therefore, developing gas detection technology that can achieve rapid, qualitative and quantitative identification and detection of harmful gases in various scenarios has become an urgent problem for researchers. With the development of spectral imaging technology, the spectroscopy method develops rapidly. Compared with the traditional gas detection method, the spectroscopy method does not require sample preparation, and is fast, non-invasive, highly-efficient and dynamic, thus suitable for rapid and continuous detection in various fields. Accordingly, the spectroscopy method has become a hot spot of research and application in various countries.

This paper first introduces the theoretical foundation of optical gas detection technology, and then reviews the working principle and application of various optical detection technologies for typical gases according to active and passive detection. Active detection methods include tunable diode laser absorption spectroscopy (TDLAS), differential absorption LiDAR (DIAL), differential optical absorption spectroscopy (DOAS), etc. Passive detection methods include remote sensing Fourier transform infrared spectroscopy (RS-FTIR) and spectral imaging (SI). This paper focuses on the applications of optical gas detection methods mentioned above. In order to facilitate a deeper understanding of the application fields of each technology, we have detailed the types of gases, accuracy, detection limits, volume and cost that can be detected in each technical, and the latest application results of each technology are introduced in detail. Using these gas detection technologies, continuous and real-time monitoring with long distance and high sensitivity for dozens of gases have been achieved, measurements of composition, concentration, temperature and other parameters of gases in a variety of scenarios have been realized, thus effectively reducing the appearances of dangerous accidents. The future development tendency of optical gas detection technologies is prospected after summarizing and analyzing the existing technologies and their problems.