Beech wood dust as obtained during abrasive belt sanding along the grain was the focus of the study. Three fractions of the dust distinctly different in particle size were analyzed. Adsorption and desorption experiments were performed with dynamic vapor sorption (DVS) apparatus. The obtained sorption isotherms were parameterized with the GAB model. The equilibrium moisture content of dust increased with decreasing particle size. A significant influence of particle size on the reduction of sorption in the monolayer was found. The monolayer capacity at 25 degrees C was ca. 0.05 kg/kg and 0.09 kg/kg for adsorption and desorption, respectively. The multilayer sorption was practically independent of temperature and particle fraction. The influence of moisture content, particle size, temperature and sorption mode on water diffusivity was determined. The highest values of water diffusivity were observed for the lowest moisture content values corresponding to the monolayer sorption. The fastest diffusion was found for wood dust moisture content corresponding to gas relative humidity up to ca. 30%. The diffusivity also increased with the diameter of dust particles. The influence of temperature on diffusivity was more distinct for the smallest particles. (C) 2019 Elsevier B.V. All rights reserved.