# Advancements and Prospects of Electronic Nose in Various Applications: A Comprehensive Review
## 3 Application Areas
### Environmental Monitoring
The e-nose system incorporated efficient algorithms for gas classification, concentration estimation, and risk threshold warnings, while considering factors such as oxygen concentration, temperature, and relative humidity. This work showcases the potential of low-cost e-nose technology to contribute to wide-area monitoring of hazardous situations in industrial settings. The developed system (see Figure 5), as reported by [PERSON] et al. [123] is designed to address the critical need for timely detection of hazardous gases in refinery environments. It employs a range of sensors, including semiconductor, catalytic, and electrochemical types, to ensure enhanced selectivity and accurate gas detection. The system's architecture includes a multifunction board for signal conditioning and data sampling, connected to a personal computer for advanced data analysis and processing. The integration of pattern recognition techniques further enhances the system's ability to discriminate between different gas mixtures. Figure 4: Map of the monitored site [122]. In contemporary environmental studies, [PERSON] et al. [124] have made a significant contribution to addressing odor emissions from waste management plants. This issue has gained regulatory attention in Italy due to environmental and economic concerns. The researchers explored the use of electronic noses to capture real-time odor emissions data. By employing various sensor technologies, including MOSs and polymer/black carbon nano composite array (NCA) sensors, along with multidisciplinary methods such as dynamic olfactometry and gas chromatography-mass spectrometry/olfactometry, the study aimed to enhance odor recognition and implement cleaner production technologies. The study identified key odor sources in waste management plants, including biogas and dehydrated sludge. A variety of sensor technologies were evaluated, achieving successful recognition rates of 86.7% for MOSs, 53.3% for NCA, and an impressive 93.3% for a subset of sensors carefully chosen based on their selectivity toward odor-active molecules. These recognition rates were determined through linear discriminant analysis and cross-validation techniques. Additionally, the research showcased the potential of electronic noses for monitoring odor abatement processes. The work by [PERSON] et al. offers valuable insights for designing effective odor control systems and advancing sustainable waste management practices. In another environmental research endeavor, [PERSON] et al. [125] conducted a critical and comparative examination of odor assessment methods at a landfill site. Through the utilization of chemical analyses, dynamic olfactometry, and electronic noses [126], the study offers valuable insights into the intricate nature of odor emissions evaluation. The authors emphasize the unique contributions of each method. While chemical analyses unveil odor composition, they do not correlate directly with dynamic olfactometry's odor concentration measurements. Olfactometric analyses offer a quantification of sensory impacts, aiding in understanding off-site effects. The study's innovative use of electronic nose technology for real-time ambient air monitoring unveils temporal odor presence percentages at landfill boundaries and receptors. Remarkably, these percentages consistently remained below the 15% limit stipulated by the German guideline \"GIRL Geruchsimmission-Richtlinie.\" [125]. [PERSON] et al. [127] present a notable advancement in odor monitoring using the EOS507F electronic nose (SACMI, Imola, Italy), developed in collaboration with the Olfactometric Laboratory of Politecnico di Milano (Figure 6). Their research is centered around developing and implementing a performance testing protocol for Instrumental Odor Monitoring Systems (IOMS). The study involves monitoring odors from a tire storage area, which experiences varying emissions over time.