Weight loss curves of two wood species (beech and Douglas fir) have been measured in air for four heating rates between 5-40 K/min and a final temperature of 873 K. A four-step series mechanism describes well the details of the thermogravimetric curves of the devolatilization/combustion process. The rates of the first three reactions are linear in the solid mass fraction and the activation energies are 106, 226 and 114 kJ/mol, respectively. The fourth step presents a power-law dependence (n = 1.54) on the solid mass fraction and an activation energy of 183 kJ/mol. Pre-exponential factors and stoichiometric coefficients take into account the differences between the two wood species. (C) 2004 Elsevier Ltd. All rights reserved.