# 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
There are also numerous studies to improve electronic nose detection performance in terms of pattern recognition algorithms for electronic nose systems. [PERSON] (2002) [21] demonstrated the electronic nose gas recognition performance, using a device composed of polymer conductive sensors to distinguish the odor of plastic parts in a vehicle, after which the first coefficient of the Fourier transform was used to build a curve using the changes in principal component analysis (PCA), which can improve the ability to discriminate the odor. This data processing method still needs to be improved. [PERSON] (2021) [22] classifies volatile gases from two industrial polypropylene (PP) materials in vehicles at different temperature gradients and proposes a deep learning method to automatically extract and classify the depth features of the raw data of the electronic nose. The deep learning method does not require pre-processing of gas information, integrates the feature extraction and classification processes, and achieves intelligent recognition of gas information of PP materials. Hazardous gases in the vehicle will affect its air quality, and an evaluation standard for the air quality in the vehicle is needed in the research process. [PERSON] (2006) [23] combined human sensory data with a MEMS sensor array system and combined the two algorithms to suppress \"false\" events, recording and classifying real data. The entire in-vehicle gas sensor system is in good agreement with human sensory impressions, laying a solid foundation for improving the applicability of the electronic nose at a later stage. [PERSON] (2020) [19] Focusing on the gas label classification problem and class evaluation in the vehicle, two multi-label classifiers based on binary correlation (BR) and classification chain (CC) are designed for distinguishing odor type and class simultaneously and for distinguishing odor type first and then class, respectively. Using a self-designed portable electronic nose, six classes of odors released from six common interior materials were detected and classified, and the experimental results showed that both multi-label classifiers achieved good recognition accuracy. Drunk driving is one of the main causes of vehicle accidents. In order to reduce the incidence of vehicle accidents, alcohol should be classified into warning gases and included in the ranks of in-vehicle gas detection. [PERSON] (2012) [36] found that the human exhaled gas contains positively charged and negatively charged water clusters, so the highly sensitive water cluster detection (WDC) respiratory sensor is designed to detect the breathing of drivers of vehicles, and it is combined with alcohol sensor to prevent drunk driving and fatigue driving. There is also research combining sensor technology with vision technology. [PERSON] (2021) [37] analyzed sensor detection and visual detection data to identify people with alcohol in their blood. We considered some criteria of intoxication status, such as alcohol concentration in the environment, the driver's face temperature, and pupil width. Once tested under real conditions, the system can detect drunk drivers with 95% accuracy. Meanwhile, [PERSON] (2020) [38] developed a real-time e-nose with a metal oxide sensor (MOS) array for monitoring five highly flammable liquids in the vehicle (ethanol, tetrahydrofuran, turpentine, paint thinner, and gasoline). The results of the qualitative analysis showed that principal component analysis (PCA) cannot effectively distinguish these samples compared with backpropagation artificial neural network (BP-ANN), and the accuracy of BP-ANN for test samples is 100%. Regression analysis was used for quantitative analysis, with an average error of 9.1%-18.4%. In addition, through anti-interference training, the electronic nose can filter out potential false positives caused by mosquito repellents, perfume, and hairspray, and its performance needs to be further improved.