Verification of the applicability of the RAD7 radon monitor to the solid radon source exhalation reference model

The RAD7 radon monitor, based on the electrostatic collection method, is sensitive to humidity during measurements, necessitating the use of a desiccant to maintain the relative humidity in its built-in chamber less than 10 %. Therefore, the gas inside the radon accumulation chamber will also be dried in closed-loop measurement. In the previous study, a solid Rn-222 source exhalation reference model was proposed, which can adjust the radon exhalation rate by adjusting the radon accumulation chamber's bottom area. In this paper, three sets of experiments were conducted to verify the applicability of RAD7 to this model. Results show that when the temperature is about 26 °C and the relative humidity inside the chamber is reduced from 71 % to 32 %, the average radon exhalation rate (43.8 ± 1.9 mBq m⁻ 2 s⁻ 1 ) aligns within one standard error of AlphaGUARD's (41.0 ± 3.5 mBq m⁻ 2 s⁻ 1 ) and the reference value (43.0 ± 0.5 mBq m⁻ 2 s⁻ 1 ), indicating that drying has almost no effect on the experimental results. Therefore, the model is suitable for verifying the accuracy of radon exhalation rates measured by RAD7, and commercially available radon exhalation measuring instruments based on electrostatic collection methods can also be calibrated using this model.