Radon in the dry carbon dioxide spa of Mátraderecske, Hungary

The final product of a post-volcanic activity is the exhalation of low-temperature (2 spas. Along its pathway to the surface, the deep origin gas also intakes different radon isotopes from the rocks and soils; therefore, the risks associated with radon exposures should also be a concern. In this work, we have found that the 222Rn activity concentration in the mofette gas of Mátraderecske is particularly high; it is in the order of 200 kBq·m−3. However, owing to the carefully designed flow pattern of mofette gas and fresh air, the radon level is about 1 kBq·m−3 at the breath level of the staff, accompanying the treatment, which is the radon reference level for workers in Hungary. We have also found that in this dry spa, radon is a good tracer of CO2; therefore, it can be used to monitor the CO2 distribution in the treatment pools.