The release of volatiles of pine wood particles was analyzed by means of continuous measurements of the CO2 and O-2 concentrations obtained after the complete combustion of the volatiles and from flame extinction times. A relatively simple mathematical model was used to predict the O-2 consumed, as a function of time, during the devolatilization and further volatiles combustion of wood. chips in fluidized beds. In this model, the drying and pyrolysis of wood particles is considered as a coupled process controlled by the kinetics of devolatilization as well as heat transfer to and through the particles. A distributed activation energy model is adopted for the kinetics of devolatilization of the wood particles. The wood chips are characterized by an equivalent particle diameter and a shape factor and transformed into spherical shape. The model was in satisfactory agreement with experimental data over a wide range of operating conditions, particle sizes and shapes, and particle moisture contents of practical importance for wood combustion in fluidized beds.