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Arni, situated in the Tiruvannamalai district of Tamil Nadu, occupies a strategic position in the Eastern Ghats foothills at approximately 12.6700°N, 79.2800°E, with an elevation around 150 meters above sea level. This inland town lies roughly 120 kilometers southwest of Chennai and 40 kilometers northeast of Vellore, placing it within Tamil Nadu's emerging industrial-textile corridor while maintaining strong agricultural connections to surrounding rural areas. The terrain transitions from the flat plains of the Palar River basin to gently undulating hills, creating a natural basin-like topography that significantly influences air quality by trapping pollutants. Arni's location away from major water bodies like the Bay of Bengal (approximately 100 kilometers east) means it lacks the moderating sea breezes that coastal cities enjoy, allowing pollution to accumulate more readily. The town sits at the intersection of agricultural zones dominated by paddy fields and groundnut cultivation with growing industrial pockets specializing in silk weaving and textile processing. This urban-rural gradient creates a complex pollution profile where agricultural burning occasionally combines with persistent industrial and urban emissions. The surrounding landscape of scrub forests and rocky outcrops provides limited natural filtration, while the town's expansion along major roadways has created linear pollution corridors that concentrate vehicular emissions.

Arni's tropical wet-and-dry climate creates distinct seasonal air quality patterns that residents must navigate carefully. During the northeast monsoon season from October to December, reduced rainfall compared to the southwest monsoon allows pollutants from silk weaving units, textile dyeing, and increased construction activity to accumulate, with November through February representing the peak pollution period. These months experience frequent temperature inversions and calm winds that trap emissions near the surface, compounded by morning fog that reacts with industrial chemicals to form secondary pollutants. Sensitive groups including children, elderly residents, and those with respiratory conditions should limit outdoor activities during morning hours in these months when pollution concentrations are highest. The southwest monsoon from June to September brings cleansing rains that temporarily improve air quality, though high humidity can make existing pollutants feel more oppressive. March to May sees extreme heat that accelerates photochemical reactions between vehicular emissions and textile chemicals, creating ground-level ozone concerns despite better atmospheric mixing. For optimal outdoor activity, the immediate post-monsoon periods of late September and early June offer relatively better conditions, while winter mornings should be avoided entirely by vulnerable populations. The cyclical drought-flood patterns further complicate this picture, with drought years seeing more construction dust and flood years potentially washing pollutants into residential areas.