Chengdu experiences significant air pollution, particularly during the winter months from October to March, when smog is most prevalent due to the city's location in the Sichuan Basin. Because the city is surrounded by mountains, pollutants often become trapped and settle for longer periods compared to coastal cities. The air quality is frequently categorized as Moderate to Poor, with real-time Air Quality Index (AQI) readings often ranging between 70 and 150, though it can spike higher during severe pollution events. Major pollutants include PM2.5, PM10, and ozone, which can cause respiratory irritation and are particularly harmful to sensitive groups like children and the elderly. While the Chinese government has made massive efforts to improve air quality since 2013, and summers often see clearer blue skies and better AQI levels, the city remains one of the more polluted urban centers in China. Visitors and residents are often advised to monitor daily AQI levels, use air purifiers indoors, and wear N95 masks when pollution levels exceed 150.