Tesfaye, Tilahun (PhD)Tesfaye, Yared2018-07-092023-11-092018-07-092023-11-092007-08http://10.90.10.223:4000/handle/123456789/7343Air was sampled by the use of suction pump through a glass filter (> 90% filtration efficiency) and aerosols were deposited on the glass-fiber filter. The aerosol deposited on the filter paper was placed below a GM tube (with GM nuclear counter) within a time interval of less than one minute after the end of sampling. The gross ¯ counts were registered in successive time intervals for more than six to ten hours (i.e. in intervals of 1 min for the first one hour; 2 min for the second hour; 4 min for the third hour etc. ) The activity concentration of progenies of 222Rn and EEC (equilibrium equivalent concentration) of 222Rn was done by fitting the observed gross ¯ count to a mathematical model derived. The indoor and outdoor variation of 222Rn was observed inside and outside of the nuclear physics laboratory (around four meters above the ground). The average EEC of 222Rn was found to be 23.9 Bq=m3 and 3.4 Bq=m3 for indoor and outdoor respectively. Indoor radon concentration is 4 to 6 times higher than the outdoor concentration. Our result agrees with the results available in other studiesenAtmospheric RadonThesis