The effectiveness of re-entrainment of particles from powder structures into air flowing through a powder aliquot placed in channel of rectangular cross-section was investigated experimentally. The shear stream of the gas causes breakage of the powder structure and particles or their clusters move to the air stream with an efficiency that depends on airflow rates and air humidity. At higher flow rates, large agglomerates are re-entrained, especially if the powder was conditioned at higher air humidity. The modifications of particles surfaces through adsorption of surfactants or electrostaticaly active substances cause the screening of the short-range cohesive forces between particles and particle processing make the re-entrainment more effective. Reduced size of particles clusters re-entrained into the air stream is also observed for modified surfaces of powder particles.