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Description
Public open caves belong to underground workplaces with radon. The average annual radon concentration in caves in the Czech Republic reaches up to 2500 Bq·m$^{-3}$. The methodology for estimation of effective dose (E) from radon for the cave guides is based on integral radon activity concentration measurement (using trace detectors RamaRn) and evidence of working hours spent in the underground in two (summer and winter) seasons. The dose conversion coefficient (DCC) has a fundamental influence on the dose calculation results. Based on ICRP 137 Recommendation, the basic DCC for workers in cave 1.33E-5 mSv/Bq·m$^{-3}$·h$^{-1}$ was adopted. When the free and attached fractions are known, individual DCC (IDCC) can be used. Change of DCF to DCC brought an increase in E and opened up the need for optimization, which has very limited possibilities in the conservative conditions of caves. Continuous radon measurement at the Peklo location has been taking place in Bozkov dolomity caves since 2003, and the measured concentrations at the Lake location form a complete set of data that was processed for the purpose of estimating and predicting movements in the earth's crust. In 2022, the number of detectors was extended to 7 locations. This unique set of data from continuous measurement lasting 4 years allows us to understand the relationship between radon activity concentration and outside temperature throughout the cave. Spatial and geological context for the measurements is provided by a 3D LiDAR model of the caves, in-situ radiometric map of the surface delineating the dolomite segment, and resistivity tomography (ARES system) results, expanding the information about individual underground spaces. This holistic approach enables optimization of effective dose estimation.