  The aim of this study is to measure the radon mass exhalation rate from
common granite building materials used in the East and Northeast part of
Portugal. Twelve cubic shaped samples were measured. Nine of them without any
coating and three coated with different materials (varnish,hydrorepellent and
liquid silicone). The radon measurements were performed with two different
techniques: one using passive detectors and other using an active detector. For
the passive method CR-39 solid state nuclear track detectors were used. The
active method used the RAD7 DURRIDGE detector. Radon mass exhalation rates
obtained from both methods present relatively low values in the 11 to 45
mBq/kg/h range for the analyzed samples. Concerning the coated samples, the
measured values are on average four times lower than the ones without coating.
Overall, the measured values for both methods present a good agreement.
