Change of ra don con cen tra tions in dwell ings with floor level was stud ied in six multi-story build ings, in four towns of Montenegro with dif fer ent cli mate con di tions. The an nual av erage ra don ac tiv ity con cen tra tions in 35 dwell ings are found to be very low, mostly at a level of 20-30 Bqm -3 . Ab sorbed gamma dose rates in these dwell ings are in the range of 14-58 nGyh -1 . The low ra don con cen tra tions are a con se quence of a good tight ness of the struc tures in con

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... t with the ground and a small con tri bu tion of build ing ma te ri als to ra don in doors. A clear gen eral trend of changes in ra don con cen tra tions with floor level is not ob served. In most of the dwell ings on dif fer ent floors in the multi-story build ing ra don con cen tra tion varies very lit tle, mostly within mea sure ment er ror. A small de crease in ra don con cen tra tion is noted be tween the two or three floors clos est to the ground, but only in some of the build ings. There fore, a de crease of in door ra don con cen tra tion with floor level can not be con sid ered as a gen eral char ac ter is tic of multi-story build ings. Al though the sea sonal ra don vari a tions have not been in the fo cus of this study, it was found that the av er age ra don ac tiv ity con cen tra tions in dwell ings of the multi-story build ings are higher in warmer than in cooler half-year pe riod, what is con trary to the gen eral rule for homes in the world and in Montenegro as well. Key words: multi-story build ing, year-long ra don mea sure ment, change of ra don con cen tra tion with floor level P. Vukoti}, et al.: Ra don Con cen tra tions in Multi-Story