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Charmahīn, nestled within the Eşfahān Province of Iran, occupies a geographically complex position significantly influencing its air quality. Located at approximately 32.3333° N, 51.1897° E, the city sits on a relatively flat plain at an elevation of roughly 1,600 meters (5,249 feet) above sea level. This elevation, while offering some scenic views of the surrounding landscape, contributes to atmospheric stability, a key factor in trapping pollutants. The city’s proximity to Eşfahān, a major industrial and population hub, is a critical determinant of its air quality profile. Charmahīn exists within a gradual urban–rural gradient, transitioning from the built environment of Eşfahān to agricultural lands and the foothills of the Zagros Mountains to the west. These agricultural zones, while providing sustenance, can also contribute to seasonal particulate matter through activities like crop burning, particularly during harvest periods. The surrounding landscape is characterized by semi-arid conditions, with sparse vegetation and limited surface water bodies. The lack of significant water sources reduces natural cleansing mechanisms for the atmosphere. Furthermore, the prevailing wind patterns, often influenced by the mountain ranges, can either disperse pollutants or, conversely, funnel them into the Charmahīn basin, exacerbating local air quality issues. The region's geological composition, with underlying sedimentary rocks, can also influence dust generation, adding to the particulate load, especially during dry periods. The city’s location within a relatively enclosed basin further limits atmospheric mixing and pollutant dispersion.

Charmahīn’s air quality exhibits a distinct seasonal pattern dictated by meteorological conditions and regional activities. Winter months (December-February) consistently present the most challenging period. Cold temperatures lead to increased residential heating reliant on fuels like natural gas and, in some cases, biomass, contributing to elevated levels of particulate matter and carbon monoxide. Critically, temperature inversions are frequent during this season, trapping pollutants close to the ground. These inversions occur when a layer of warm air sits above cooler air, preventing vertical mixing. Spring (March-May) brings a slight improvement as temperatures rise and wind speeds increase, aiding in pollutant dispersal. However, agricultural activities, including controlled burns for land preparation, can introduce significant particulate matter during this transition period. Summer (June-August) generally sees the best air quality due to higher temperatures, stronger winds, and increased convective mixing. However, dust storms originating from the surrounding deserts can occasionally impact the city. Autumn (September-November) marks a gradual deterioration as temperatures cool, and the likelihood of inversions increases. The harvest season also contributes to particulate pollution. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during winter and early spring, limiting outdoor exertion during periods of stagnant air. During dust storm events, wearing a properly fitted mask is recommended. Maintaining indoor air quality through ventilation and air purification can also mitigate exposure.