Several tests using pure bottle-grade polyvinyl chlorine (PVC), with wood (pine) and with Polish coal have been performed in a two-stage combustion test facility which contains two reactors. The first reactor is a bubbling fluidized bed (BFB) where the fuel is pyrolysed in the temperature range 200-400 °C. The second reactor is a circulating fluidized bed (CFB) operated at a temperature of around 800 °C. The pyrolysed gases from the BFB reactor or the circulating fluidized bed combustor (CFBC) are analysed with a Fourier transform infrared (FT-IR) spectrometer. The main part of this work concentrates on the first stage of decomposition of PVC in the first reactor, which mainly yields volatiles (mainly HCl) and solid residue. The results show that there is an interaction in PVC/wood pine mixtures, which affects the degradation of PVC. The same interaction also occurred with the PVC/Polish coal mixture. For the two-stage combustion test, the chemical analysis of char samples taken from the bed of the first reactor, when 100% PVC is used, shows that the chlorine content is below 0.1 wt.% at chlorine to carbon mass ratio<0.001 kg Cl/kg C.