Results of modelling gas evolution during thermal decomposition of solids (EGA) are presented. The model assumes two components in the reaction system with a random nucleation mechanism being used in the simulation of EGA and ETA curves. It was demonstrated how the shapes of the EGA and ETA curves reflect the mechanism of the thermal decomposition reaction. Three model cases of morphology changes of solid samples accompanying thermal decomposition are presented to demonstrate the possible supplementary information gained from ETA.