One of the occupational risks of mining ore results from the exposure of miners to airborne radon gases (222Rn, 220Rn) and their short-lived decay products (radon daughters). The inhalation of these radionuclides constitutes the most important occupational exposure in mines, especially in uranium mines. A previous report of the ICRP outlined the principles of monitoring and limitation of radiation exposure in uranium and other mines (IC 77b). It should be noted that radon and its daughters are also present in atmospheric and room air. The inhalation of these radionuclides constitutes a substantial fraction of the radiation exposure of the population from natural radiation sources.