A 222Rn survey was carried out in order to explore the pattern of geographical and seasonal changes of 222Rn activity in soil-gas at different locations in Chitradurga district of Karnataka State using RAD7 radon detector coupled with special accessories, without dilution by outside air technique. Radon activity in the soil gas varied from 0.5 to 812.9 (mean: 93.78 Bq/m3) and 0.8 to 810.4 Bq/m3 (mean: 92.84 Bq/m3) during pre-and postmonsoon seasons respectively, with an annual mean of 0.65 to 811.65 Bq/m3 (mean: 93.31 Bq/m3). A significant spatial and insignificant temporal variation in soil radon activity has been observed in the study area, which is in the order of Hosadurga taluk (346.56 Bq/m3)> Hiriyur taluk (95.10 Bq/m3)> Challakere taluk (36.45 Bq/m3)> Chitradurga taluk (20.40 Bq/m3)> Holalkere taluk (2.87 Bq/m3). The results showed the radon values in the soil-gas of Chitradurga district are low (< 0.8 kBq/m3) enough to categorize them under low radon risk areas (viz., 10 kBq/m3)
