Solid State Nuclear Track Detector (SSNTD) is used to determine the Radon, Thoron and its progeny concentration. Dosimeters are suspended indoor at the height of 2.5m from the ground surface. Radon, Thoron and its progeny concentration around the thermal power plant and steel plant dwellings near Bellary of Bellary District is noticed above the average level the value. The value of concentrations of radon and thoron in the area study varies from 111.7 Bqm -3 to 467 .3 Bqm-3 and 16 to 510 Bqm-3 respectively. This is because the main source of radon is burning of coal. Fly ash contains higher radioactive radon nuclides. Radioactive Radon gas causes lung cancer. According to WHO and EPA studies radon is the second largest causes lung cancer after smoking. The main study is to estimate the indoor inhalation dose radon, thoron and their progeny around the thermal power plant and steel plant indoor dwellings.