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Companiganj occupies a distinctive position within Bangladesh's Chattogram Division, situated at coordinates 22.8730°N, 91.2782°E along the southeastern coastal plains of South Asia. This municipality lies approximately 30 kilometers northwest of Chattogram city, placing it within the broader Chattogram metropolitan influence zone while maintaining its own urban character. The terrain is predominantly flat alluvial plain, typical of the Ganges-Brahmaputra delta region, with elevations rarely exceeding 10 meters above sea level. Companiganj's proximity to the Karnaphuli River and Bay of Bengal significantly influences its microclimate and pollution dispersion patterns. The urban area represents a transitional zone between Chattogram's industrial belt to the south and the agricultural hinterlands to the north, creating a complex urban-rural gradient where pollution sources intermix. Surrounding landscapes include rice paddies, aquaculture ponds, and scattered brick kilns that contribute to the particulate matter load. The city's location in the lower Meghna estuary region means it experiences both marine and terrestrial air masses, with pollution often trapped during certain meteorological conditions. Road networks connecting to Chattogram port and industrial zones generate significant vehicular emissions, while the flat topography offers little natural barrier to pollution transport from neighboring industrial areas. The combination of high population density, proximity to major transportation corridors, and mixed land use creates a challenging air quality environment where local emissions combine with regional pollution transported from the greater Chattogram metropolitan area.

Companiganj experiences distinct seasonal air quality patterns shaped by the South Asian monsoon cycle. During winter (December-February), cool temperatures and frequent temperature inversions trap pollutants close to the ground, creating the year's worst air quality conditions. Morning fog combines with smoke from heating sources and brick kilns, reducing visibility and increasing particulate concentrations. Sensitive groups should limit outdoor activities during these months, particularly in early mornings when inversion layers are strongest. Spring (March-May) brings rising temperatures and pre-monsoon dust storms that can temporarily worsen air quality, though increasing wind speeds generally improve dispersion. The summer monsoon (June-September) offers the cleanest air as heavy rains wash pollutants from the atmosphere and consistent southwesterly winds disperse emissions. This period represents the optimal time for outdoor activities, though high humidity can make breathing uncomfortable for those with respiratory conditions. Autumn (October-November) sees a gradual deterioration as monsoon rains cease and agricultural burning begins in surrounding areas, with pollution building toward winter peaks. Throughout the year, wind patterns shifting between marine and continental air masses create daily variations, with sea breezes typically bringing cleaner air in afternoons. Sensitive individuals should monitor local air quality reports year-round and consider using masks during peak pollution periods, especially when engaging in strenuous outdoor activities.