A comprehensive review of the performance of optical techniques in the sensing of pollutant gases

Optical gas-sensing technologies offer distinct advantages and limitations, making them essential for applications in environmental monitoring, industrial safety, and healthcare. This review presents a comparative analysis of optical gas sensors classified according to their operating mechanisms (spectroscopic, chemical, and electronic) and technological platforms (fiber-optic, dye-based, carbon-based, and waveguide structures). Sensor performance is evaluated using key metrics, including sensitivity, selectivity, response time, environmental stability, durability, fabrication cost, and calibration requirements. Spectroscopic techniques such as tunable diode laser absorption spectroscopy (TDLAS) and Fourier-transform infrared (FTIR) spectroscopy achieve exceptional sensitivity (