Gas sensors play a pivotal role in diverse applications, including environmental monitoring, industrial safety, medical diagnostics, and smart technologies. This chapter provides an in-depth exploration of gas sensing mechanisms employed in diverse platforms, including metal oxide semiconductors, optical systems, electrochemical sensors, acoustic devices, and fiber-optic technologies. The influence of material characteristics such as morphology, surface area, porosity, and defect states on critical performance parameters like sensitivity, selectivity, response time, and long-term stability is extensively analyzed. Advanced strategies for performance enhancement, including nanostructure engineering, heterojunction formation, surface functionalization, and optimized electrode configurations, are systematically reviewed. The chapter also discusses using AI/ML to enhance selectivity, correct drift, and enable real-time analysis, along with the role of multisensor arrays and e-noses in detecting complex gas mixtures. The conclusion highlights future focus on compact, smart, energy-efficient gas sensors integrated with IoT and wearables for advanced diagnostics and environmental monitoring.
