The dynamics of microstructural variations in smokes of pyrolysis origin at their relaxation in a closed volume is considered by comparing the diagrams of polarization measurements of aerosol scattering parameters with the model estimates. From the analysis of experimental data, peculiarities in transformation of the disperse composition of pyrolysis smokes were noticed in different ranges of the size spectrum. It is found that smoke particle number density at smoke generation is a scaling factor in formation of smoke optical and microphysical characteristics. The dynamics of parameters of the microdisperse fraction follows the typical coagulation variation of a spectrum with the shift of the modal radius from r1m(3) = 0.042 mm at the initial stage of measurements to r1m(3) = 0.075 mm (particle enlargement) in two hours. At the same time, the coarse-disperse fraction is characterized by significant decrease in both the particle number density and the volume concentration while the modal radius r3m(3) shifts insignificantly from 1.09 to 0.869 mm and the distribution mode relatively narrows. The latter may be caused by an increase in compactness of the morphological structure of large smoke particles. The process of large particles sedimentation upon the chamber walls prevails over the processes of coagulation enlargement, thus causing the marked decrease in the particle number density in this range of the particle size spectrum.