Measurement and Analysis of Air Quality in Rail Transit Systems: A Case Study of the Istanbul Metro

Rail transit systems are preferred worldwide for their convenience, safety, and speed. However, their enclosed environments feature high particulate matter (PM) concentrations and diverse particulate content. PM concentration varies due to factors such as outdoor air quality, tunnel design, the chemical composition of rail components (wheels, tracks, braking systems, power sources), power systems, braking mechanisms, train speed and frequency, passenger numbers, ventilation and air conditioning systems, cleaning frequency, and other operational conditions. The Istanbul rail transit system transports over 2 million passengers daily, accounting for approximately 20% of the city's transportation load. This study aims to assess current air quality in the Istanbul rail transit system and observe the effects of platform screen doors and ventilation systems. Measurements were conducted at 7 underground stations, including PM₁ (particles smaller than 1 micron), PM_2,5 (particles smaller than 2.5 microns), and PM₁₀ (particles smaller than 10 microns), as well as thermal comfort parameters (temperature, humidity, air flow rate) and gas measurements (CO and CO₂). The results indicate that controlling the content of rail transit dust can significantly improve air quality.