Complementary thermal analytical techniques were used to analyze gaseous products evolved during the co-firing of coal with refuse derived, fuels. The combined thermogravimetric (TG)/Fourier transform infrared (FTIR)/mass spectrometry (MS) techniques were employed to study the reaction pathways for the formation of gaseous products during combustion, as well as identify molecular chlorine, HCl, CO, CO2, H2O and various organic compounds. The discovery of molecular chlorine has led us to look for the possible formation of chlorinated organic compounds in the combustion process. Chlorine and hydrocarbon species are released in the same temperature range and in higher concentrations during fast heating rates compared to relatively slow ones. These results indicate that there may be more opportunities to form chlorinated organic compounds during the co-firing of coals with refuse-derived fuels (RDF) at the faster heating rates that may occur in a fluidized-bed combustor (FBC) system.