This paper deals with the laboratory scale identification of the formation and growth of fine particles during the temperature increase of beech wood samples. The utilized experimental procedure combines the thermogravimetric analysis and identification of particles in flue gas leaving the thermogravimetric analyser (TGA). The aerosol stream leaving TGA enters a Scanning Mobility Particle Sizer (SMPS) where the particle size fractions are separated. The number of particles is identified by the condensation particle counter (CPC). The parametrical study was carried out to assess the composition of the atmosphere on the production and size distribution of fine particles during a heating of beech wood samples. There is clear evidence that the increase of oxygen content in the atmosphere generally results in the lower mass concentration of produced particles.