A new fluidized bed thermogravimetric analyzer (FB-TGA) was developed that introduces two major particularities: the pseudo variation of the weight of the reactor and the special strategy for gas flow rate adjustment according to temperature. A momentum balance was performed on the reactor and the pseudo variation of the reactor weight was evaluated by measuring the pressure drop through the gas distributor and filter. The real weight loss of the reactor was obtained by subtracting the pseudo variation of the weight from the total weight loss measured by the load cell. In addition, a special program for the gas flow rate as a function of temperature was developed and used; so the minimum fluidization regime is maintained throughout all of the experiments. The validation test of the FB-TGA was carried out on calcium hydroxide decomposition, and the results were compared with those obtained from the conventional TGA. Diffusion control was suppressed by the application of the FB-TGA, which was confirmed by the x-ray diffraction analysis on the treated samples. (c) 2014 American Institute of Chemical Engineers AIChE J, 61: 84-89, 2015