[en] For approx. 2 yr cellulose triacetate film (Bexford-125, Bexford Ltd., England) was used as a passive track detector (PTD) to monitor miners' exposure to radon and its daughters in three mines; two zinc-lead and one copper. The detector was applied as an environmental cassette, hung on work posts in the mines, and as a helmet cassette, attached to the miner's helmet. For comparison, air sampling measurements were taken where the environmental cassettes were hung and where miners wearing helmet cassettes worked. Results of the 2-yr investigation showed that appropriately calibrated passive track detectors can be used in place of conventional air sampling methods to evaluate occupational radiation hazards in mines. (author)