[en] The indoor behavior of the radon decay products were evaluated considering the relative activity particle size distribution and also the activity concentration. It is evident from the present study activity concentration as well as the particle size distribution varies considerably. Relatively high radon concentrations were observed at homes with a widen shape of the particle size distribution but in the case of workplaces, low F value is obtained as the decay product did not grow sufficiently due to the large interchange of air through personnel movement and adequate ventilation. The estimated average effective dose for work place and home also found to be much lower than the dose referred in UNSCEAR report 1993 as 1.2 mSv. (N.C.)