en Radiation Biology Radiation Biology تحقيق بديع Original Research <span style="font-weight: bold">Background:</span> Radon and its daughter product are a major source of natural radiation exposure, the measurement of radon concentration in dwellings is assuming ever increasing importance. It is known from recent surveys in many countries that radon and its progeny contributes significantly to total inhalation dose and is well established that radon when inhaled in large quantity causes lung disorder. In view of this the authors have measured ²²²Rn and ²²⁰Rn levels in dwellings of different volumes at Bangalore Metropolitan, India. <span style="font-weight: bold">Materials and Methods:</span> Integrated and long duration measurements of radon were carried out using twin cup dosimeters with Solid State Nuclear Track Detector technique. <span style="font-weight: bold">Results:</span> Results showed that concentrations of ²²²Rn, ²²⁰Rn, their progenies and dose rates in dwellings decreased with increase in room volume. Conclusions: The annual effective inhalation dose due to ²²²Rn, ²²⁰Rn and their progenies from the study ranged between 0.2–4.4 with an arithmetic mean of 1.7 ± 1.1 mSv y^-1. The dwellers of lower volumes are posed to high dose rates. <span style="font-weight: bold">Iran. J. Radiat. Res., 2012 9(4): 231-236 </span> 222Rn, 220Rn, room volume, dose rate 231 236 http://ijrr.com/browse.php?a_code=A-10-1-407&slc_lang=en&sid=1 L.A. Sathish lasgayit@yahoo.com 790031947532846002455 790031947532846002455 Yes K. Nagaraja 790031947532846002456 790031947532846002456 No