Radon (Rn-222) is a noble gas and is present in trace amounts almost everywhere on the earth. It escapes from rock, soil or groundwater containing Radiun-226 in different concentrations. Radon can also originate from a deeply buried deposit and can migrate to the surface of earth by diffusion and transport process. It can accumulate in enclosures like rooms, caves, cellars and basements since it has a fairly long half life. The increased interest in indoor Radon concentration is due to its health hazard and environmental pollution. In the present study measurements of indoor Radon levels in Bharatpur (Rajasthan) have been made. For this LR-115 plastic track detectors were used. The average potential alpha energy level measured is found to vary from 12.60 mWL to 28.39 mWL. The average internal exposure dose to the tracheobronchial and pulmonary regions of lungs shows a variation from 3.97 m SvYr -1 to 8.94 m SvYr -1 .

Radon, Progeny, Dwellings, SSNTDs, Radon activity, Etching, Alpha tracks.