A specialist computer software was used to simulate changes in chem. compds. of gases (CO, CO2, H-2, MeH) formed by pyrolysis (850 degrees C, residence time 2-8 s) of refuse-derived fuel (RDF) with a fixed computations. The comps. of gases were compared with literature exp. data. The large convergence for both types of results was achieved. The changes in the content of other compds. present in post reactions gases (hydrocarbons, including polyclic arom. ones, and S and Cl-contg. compds.) were forecasted to limit potential hazards caused by using RDF.