# Development Trend of Electronic Nose Technology in Closed Cabins Gas Detection: A Review
## 4 Application of Electronic Nose in Gas Detection of Closed Cabins
### Gas Detection in Vehicle Cabin  
In the past few years, different types of electronic noses, as well as sensor arrays, have been proposed for the detection of various types of gases in vehicles [6; 16; 20]. The first and foremost detection of hazardous gases in vehicles is the detection of VOCs in vehicles, and interior materials are the main source of VOCs in vehicles, and related research revolves around this. Gas sensors are an important part of the electronic nose system, and dozens of types have been developed over the years, but not all of them are suitable for gas detection in closed cabins. [PERSON] and [PERSON] (2000) [16] compared the ability of three sensors to distinguish five polyurethane materials in a closed vehicle cabin, and the results showed that the conductive polymer sensor (CP) could not accurately distinguish polyurethane foam, while the use of metal oxide sensor (MOS) combined with multiple discriminant analysis (MDA) method could obtain satisfactory results with 91% identification accuracy; meanwhile, the experiment proves that when MOSFE sensor and MOS sensor are combined to detect the sample, the recognition probability is improved to a certain extent. [PERSON] (2000) [6] Using a MOSFET sensor in combination with a MOS sensor, the data were processed using a principal component analysis (PCA) multivariate approach, and the  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & **Sensor** & **Application** & **Analysis Method** & **References** \\ \hline \multirow{4}{*}{Gaseous tricrresyl phosphate (TCP) in aircraft cabin} & \multicolumn{4}{c}{The application of electrode antifouling modifiers of continuous detection (TCP)} & \multirow{4}{*}{CV curve} & \multirow{4}{*}{[24]} \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\   Simulated electric steam fire & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & &  
processed data were compared with gas chromatography-mass spectrometry (GC-MS) and human sensory panel data, respectively, and concluded that the electronic nose combined with pattern recognition can more easily detect deviated samples with abnormal emission gases to detect vehicle interior material gas emission anomalies. This paper demonstrates the superiority of the e-nose over GC-MS, and it is the first paper to propose the combination of human sensory analysis with e-nose technology to improve the performance of e-nose in-vehicle gas detection. Similarly, [PERSON] (2003) [20] analyzed vehicle seat materials using three methods: e-nose, sensory analysis, and GC-MS, and explored the link between e-nose and sensory attributes by setting e-nose and sensory analysis data as activation variables and different detection methods as explanatory variables, thus providing new ideas for subsequent studies. Many of the above-researched gas sensors are utilized without disassembling the existing sensors. To improve the reflective sensitivity of the existing gas sensors, [PERSON] (2008) [18] studied a suitable semiconductor metal oxide, that is, tungsten oxide (WO3) material was used as the surface layer of the gas sensor, and the sensitivity of the sensor was finally tested by gas sensitivity test. The characterization results were consistent with the previously verified analysis model. The feasibility of the proposed micro-hot plate silicon gas sensor for gas detection in the vehicle is demonstrated. Some studies propose a novel cavity design starting from the design structure of the cavity, [PERSON] (2020) [17] considered the shape and size of the in-vehicle gas sensor, and the core design idea was to reduce the space for airflow in the electronic nose and adopted a series of cylindrical structure designs. The sensor, which compresses the headspace, and computational fluid dynamics (CFD)-based simulations show that the concentration of pre-concentrated gas in the novel chamber is higher than in conventional chambers.