Pyrolysis experiments were performed between 800 degrees C and 950 degrees C on wood particles with diameters from 350 to 800 mu m in a lab-scale drop tube reactor to reproduce surface heat flux representative of gasifiers conditions. It was shown that particle size affected the required pyrolysis time but changed neither gas/tar/char mass yields nor composition of the products at the end of pyrolysis. The initial particle size also affected the resulting char morphology: the larger the biomass particles, the more fibrous the char. Temperature had influence neither on gas/tar/char mass yields nor on gas and solid elemental composition at the end of pyrolysis, but significantly changed the yields of individual gas species. Whatever the conditions tested, a significant shrinkage could be observed on particles during pyrolysis. These experimental results confirm the strong coupling between chemical reactions, particle geometrical properties and heat transfers during pyrolysis under these conditions. (C) 2012 Elsevier Ltd. All rights reserved.