Alpha- and beta-activities per unit volume of air due to radon (222Rn), thoron (220Rn) and their progenies were measured in the air of natural caves and ancient mines as well as inside different reference
atmospheres by using CR-39 and LR-115 type II solid state nuclear track detectors (SSNTDs). In addition, the radon concentration
was continuously measured inside one of the studied caves by using the SSNTDs’ method and AlphaGuard counter. Equilibrium
factors between radon and its daughters and between thoron and its progeny were evaluated in the studied atmospheres. Alpha-activities
due to 218Po and 214Po short-lived radon decay products were determined in different compartments of the respiratory tract of members of the public.
The committed equivalent doses due to the 218Po and 214Po radon short-lived progeny were evaluated in different tissues of the respiratory tract of the visitors of the considered
caves and ancient mines. Annual effective doses due to radon progeny from the inhalation of air by the visitors of the studied
caves and ancient mines were evaluated.