In 1168, the first silver was found in the Saxon Erzgebirge. Mining began shortly thereafter and continues to this day at varying intensities. About 250 miners are permanently engaged in rehabilitation work at old mining sites so that houses and roads are safe and the mine water can drain through galleries. The radon potential in the Erzgebirge is high. Despite radiation protection measures, exposures to more than 6 mSv occurred among 22 miners in 2016 alone. For this reason, the miners are monitored with personal radon dosimetry. The dosimeters consist of diffusion chambers with CR-39 nuclear track detectors. Outside the miners’ working hours, the dosimeters must be stored together with a reference dosimeter. After a 3 mo wearing period, the dosimeters are replaced and the miners’ exposures are determined. For this purpose, the exposures of the reference dosimeters that have occurred outside working hours are subtracted from the exposures of the miners’ dosimeters. In mining practices, this method has caused problems. The conditions of use (storing dosimeters along with a reference dosimeter) were often not met by the miners. To solve the problems, reference dosimeters were replaced by radonproof boxes with activated carbon cartridges inside. The miners stored their dosimeters in the boxes outside working hours. A uniform reference value for the radon activity concentration of 50 Bq m −3 was used for all boxes to determine the exposure of miners during working hours. The associated error was small. In future, reference dosimeters and the measurement of a reference value will not be necessary.

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In the National Board of Nuclear Safety and Radiation Protection of the GDR solid state nuclear track detectors (SSNTD) have been used routinely both for individual neutron dosimetry and for long-term measurements of radon and radon daughter products in flats and in the environment. For neutron monitoring a fission track dosemeter is used for the simultaneous response to fast and intermediate neutrons, using Makrofol KG as a detector. The long-term dosemeter for registering radon and radon daughter products is based on the diffusion chamber principle. Makrofol DE 1-4 of 300 µm thickness is used as the detector. Detector evaluation and calibration methods are described in detail and detection limits are stated. In addition, a screening measuring method based on CR-39 is presented, allowing the rational performance of long-term measurements by radon diffusion chambers.