[en] Deep seated fluids generate remarkable geochemical processes when forced toward the earth's surface. Intense water-gas-rock interaction reactions characterise fluid motion in the earth's crust due to changes in pressure-volume-temperature conditions. Due to their chemical characteristics noble gases have been indicated as tracers of fluid dynamic changes. Among them ²²²Rn plays an important role due to wide distribution of U, and to low cost monitoring equipment. A correct understanding of transport phenomena is crucially important in data interpretation. The general features of ²²²Rn migration processes are discussed. (author)