The paper presents the most recent data, collected in 1990/92, on concentrations of ²²²Rn products in the air of all Polish underground non-uranium mines data on the exposure of the miners employed there. The concentrations and exposure of miners were evaluated by using "passive" dosimeters, based on the track-etch solid state nuclear track detector, worn as small individual cassettes on helmets of representative groups in every mine for one month, four times a year (once in each season of the year). This paper contains the average annual exposure of miners in coal-, metal-ore-, and chemical raw materials mines. The paper also presents the expected "frequency" distributions of individual miners' exposure in particular types of mines, as well as the computer simulations of "relative frequency" distributions of expected miner's exposure if the Annual Limit of Exposure were adopted at the level 17, 12, 8.6, 6.9 and 3.4 mJhm^-3 (5.0, 3.5, 2.5, 2 and 1 WLM). The concept and criteria for the classification of mines according to the radiation hazards are presented and discussed. According to this concept, all mines in Poland have been considered and classified into four classes of mines with different levels of radiation hazard. The appropriate radiological surveillance for the respective class of mine is proposed and discussed.