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 11–45 mBq kg−1 h−1 range for the analysed 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.

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