Setup and procedure for routine measurements of radon exhalation rates of building materials

A practical procedure and the necessary setup for routine measurement of the exhalation rate of 222Rn from building materials are described. The setup comprises a continuous radon monitor, based on an ionization chamber, and a relatively large-volume accumulation chamber. The experimentalist can interact with the setup in real time via a PC. Therefore it is possible to determine the exhalation rates by determining the optimum accumulation time before the effects of back-diffusion and radon decay set in. This, in turn, reduces the time required to test a sample and makes the setup useful for routine measurements. The exhalation rate values (Bq m−2 h−1) for selected building materials made from gypsum, marble, ceramic, and granite were found to be 1.63, 2.29, 3.99 and 5.39 Bq m−2 h−1, respectively. The optimal test-times for the samples ranged from 9 to 19 h.