Spatial variability of indoor radon concentration in schools: implications on radon measurement protocols

The requirements about radon measurements in schools and public buildings included in most of the national and international legislations are generally restricted to certain areas (i.e., radon priority areas) and/or to all the occupied rooms located at ground floor and basement, assuming the soil beneath the building as the main source of indoor radon. In order to assess the quality of such assumption, a study was performed in the framework of a radon survey carried out in 82 buildings (mostly schools and kindergartens) located in 15 Municipalities of Republic of Srpska. Annual radon concentrations have been measured in a total of 185 rooms, some of them (45) located at first floor. In order to minimize the uncertainties due to seasonal variations, the measurement period for radon devices was of one year. Preliminary results of this study show that in 25% of buildings with more than one floor monitored, average radon concentration was higher at first floor than at ground floor. As expected, variability among rooms at the same floor is higher at ground-floor (median CV=22%) than at first floor (median CV=14%). Even if most of the rooms exceeding 300 Bq m–3(the maximum reference level established by 2013/59/Euratom Directive) were located at ground floor (30 out of 32), in one building an exceedance was found at first floor only. These results, if confirmed by further studies, would suggest including in measurement protocols also requirements for rooms located at upper floors: in fact, in some multi-storey buildings, the stack effect and the contribution of building materials may lead to high radon levels also (and sometimes only) at floors not in direct contact with the soil.