# Development Trend of Electronic Nose Technology in Closed Cabins Gas Detection: A Review
## 5 Challenges and Future Trends  
Since 1982 [5], electronic nose technology has been used in various industries to ensure safety in closed chambers and to avoid any accidental release of volatile organic compounds into the surrounding environment. The main challenge for the future is to further explore the potential applications of e-noses with extended research efforts and scientific investigations. For example, as a portable, simple and accurate identification sensing device, the electronic nose can be used to identify multiple types of gases in closed cabins. Based on the signal from the electronic nose sensor, the data is then processed by filtering and noise reduction, feature extraction, and data clustering to obtain better gas recognition capability. The high-speed development of different sensors and the progress of various pattern recognition algorithms make the electronic nose, as well as the development of an efficient and portable gas detection method, have been applied to the gas detection of various closed chambers. However, single component recognition has never been the strong point of the electronic nose, and it cannot consider the influence of multiple environmental factors on the sense of smell [61]. Although electronic noses cannot completely replace traditional instruments such as gas chromatography, they can fill in the gaps to achieve real-time monitoring of gases in closed cabins. In addition, new electronic nose technologies are beginning to generate new ways of combining electronic noses with traditional analytical instruments to overcome their technical shortcomings, such as their inability to identify a single gas. At this stage, there is still room for progress in olfactory stimulation with electronic noses [62; 63]. Although the application of the electronic nose still faces the complexity of the detection environment and its performance limitations, various research work has been carried out around it. At present, the electronic nose has been in close contact with various industrial manufacturers, but it still has to face the hesitation of various manufacturers in upgrading the sensing technology and algorithm recognition. The application of an electronic nose in the closed chamber should take into account the influence of its boundary characteristics, environmental impact, and the uniformity of gas concentration, closed chamber gas detection, relying on the design of electronic nose sensors, which can be utilized for a long time with durability. Therefore, in the future, we must focus on the core issue of sensor selection when optimizing electronic noses. However, this approach requires a high degree of stability of the algorithmic model to solve the selectivity problem for all types of sensor array changes. With the development of e-nose technology, more and more commercial e-noses are developed. Only by upgrading and optimizing the existing e-nose can we help the e-nose to be utilized to the maximum extent and realize the wide application of commercial e-nose. In this era of rapid development of artificial intelligence and 5G network, the application of wireless e-nose will be beneficial to achieve accurate and real-time monitoring of closed cabins [64; 65]. In this era of artificial intelligence and 5G network development, the application of wireless e-nose will facilitate the accurate and real-time monitoring of closed chambers. The innovation of nanotechnology also provides a potential development for the e-nose [66; 67]. Its application in the electronic nose will greatly reduce the size and improve the detection level of the sensor to enhance its application in the closed chamber. Therefore, the electronic nose is essential for the application of gas detection in closed chambers, mainly for closed chamber gas detection to improve the safety of its operation. Furthermore, to certify real-time analysis and production practices, researchers should be motivated to develop suitable technologies to be integrated into the application of electronic noses.