Horizontal and vertical distribution of 222Rn and 220Rn in a dwelling, Bangalore, India

The 222Rn and 220Rn have been identified as potential radiological health hazards and the dose estimation due to their exposure is an important task. Understanding their behavior in indoor environment helps in calculating the inhalation doses due to them. Effective doses due to inhalation of indoor 222Rn and its progeny account on an average for about one-half of all natural sources of radiation. However, recently the indoor surveys in Asia revealed that the dose contribution from 220Rn and its progeny can be equal to or even exceed that of 222Rn and its progeny. In view of this an attempt has been made to observe the distribution of 222Rn and 220Rn levels in a typical dwelling for the environment of Bangalore Metropolitan, India. Present study aims at the distribution of 222Rn and 220Rn concentrations in a typical dwelling. Higher concentrations were observed at the wall and flooring of the room and the concentrations were found to decrease as the detector is moved away from walls and floorings. The concentration of 222Rn is found to be invariant in indoor environment. An attempt has also been made to study the horizontal and vertical distribution pattern of 220Rn in a dwelling. The 220Rn concentration is found to drop exponentially as a function of distance from the source (wall/floor). Solution of one dimensional diffusion equation is used for regression fittings for 220Rn variation, from which the diffusion constants and the exhalation rates were calculated. The diffusion constants varied from 0.00195 to 0.00540 m2s-1. Results are discussed in detail