Basic investigations using three different fuels as well as fuel blends have been performed in an atmospheric tube furnace at 1500 degrees C under gasification like conditions. Molecular Beam Mass Spectrometry has been used for on-line analysis of the hot product gas. Main vapour species were H2S, HCl, KOH, NaCl, COS, and KCl. After quantification of the data the release behaviour was correlated to the fuel composition. The released amount of HCl, NaCl, H2S and COS of the blends hard coal/ petroleum coke can be predicted by calculation. This can be explained by simple dilution effect. The released amount of HCl and NaCl of the blends hard coal/ refinery residue can be predicted by calculation, but the released amount of H2S and COS cannot be predicted. (C) 2014 Elsevier Ltd. All rights reserved.