Quantitative thermogravimetry-mass spectrometry (TG-MS) method was developed for the determination of the composition of gases evolved during the decomposition of solids. The present method is based on the linear relationship between the amount of evolved gases and the peak area for corresponding fragment ion via proportionality constant (K) which gains the similar values for all' evolved gaseous products. Determination and verification of K were performed with the various initial mass of CaC(2)O4 center dot H2O decomposing with the evolution of H2O, CO, and CO2. The resulted values of the proportionality constants reach (3.32 +/- 0.11) x 10(7) for H2O, (3.35 +/- 0.08) x 10(7) for CO, and (3.27 +/- 0.07) x 10(7) for CO2. The developed TG-MS method was verified at the decomposition of (COOH)(2)center dot 2H(2)O, NaHCO3 and HCOONa. By applying the average value of K for the determination of the composition of gaseous products evolved from the previously mentioned three substances, a quite good correspondence between theoretically and experimentally calculated composition can be found. The results imply that developed TG-MS method might be a useful tool to detect quantitatively the amount of evolved gases during the thermal decomposition of carbonaceous materials. (C) 2016 Elsevier B.V. All rights reserved.