The study aimed to evaluate the level of air contamination in the area around the Kosogorsky industrial enterprise in Tula, Russia, in the winter of 2021/2022. For the study, Pleurozium schreberi, Sphagnum fallax, and Dicranum polysetum mosses were used for the first time in the 3-month active biomonitoring (moss-bag technique). Heavy metals elements (Mn, Fe, Ni, Cu, Zn, Cd, and Pb) were determined using atomic absorption spectrometry. In addition, mercury concentrations were determined with an AMA254 apparatus. The study's results for Fe, Cu, Zn, Pb, and Hg confirm the statistical significance of the species' effect on the accumulation of these elements. Values of relative accumulation factor (RAF) > 1.00 at selected measurement points indicate that the site is contaminated as a result of industrial activities (mainly Mn and Fe). Wind direction influenced moss contamination at selected measurement points, which was confirmed by cluster analysis. In the future, long-term or different seasons biomonitoring studies should be conducted in this area.