Indoor measurements of 220Rn and 222Rn and their decay products in a Mediterranean climate area

Abstract

A research program on characteristics of radon exposure in dwellings in Rome was executed. The results of measurements of 220Rn gas concentration, besides 222Rn and their decay product concentrations, are reported. These measurements were carried out in the sitting-room of six dwellings, for 2-d periods in spring 1995, under normal living conditions. The 220Rn concentration was measured at about 1 cm from the wall, using the method of delayed coincidences between 220Rn and 216Po decays. The average value in the dwellings ranged from 5 Bq/m 3 to about 1100 Bq/m 3. The average 222Rn and 220Rn equivalent equilibrium concentrations, measured in the middle of the room, were within 8–43 Bq/m 3 and 0.5–9.5 Bq/m 3, respectively. The average potential alpha energy concentration ratio between 220Rn and 222Rn was within 0.9-4.6. The average equilibrium factor of 222Rn ranged from 0.42 to 0.55. The estimate of effective doses is also discussed. These results confirm the significant presence of 220Rn (thoron) and its decay products and the role of certain natural building materials used in some Italian Regions, not only as gamma and 222Rn sources, but also as 220Rn sources.