Abstract:Regular calibration of radon-measuring instruments is key to ensuring the accuracy and reliability of measurement results. Based on the internationally recognized measuring instrument AlphaGUARD P2000F and its own water raft measurement components, calibration experiments were carried out on three sets of DDL-1 ionization detectors using dissolved radon in water. The experimental and calibration results with the solid radon source were compared with those of the out-of-factory results. It was found that the relative errors of the K values of the two calibration methods were less than 5%, which meets the requirement of current seismic monitoring techniques. These results showed that the solution of dissolved radon in water, compared with the solid radon source, solved the problems of transportation difficulties, high technical maintenance requirements, strict supervision of national environmental protection departments, etc., and defined a new approach to the calibration of seismic radon observation instruments.