[en] Gas desorption from the surface of high-dispersity (S_sp=5-15 m²/g) tungsten and molybdenum powders is investigated. O₂, H₂O detected by H₂ mass-spectroscopy are absorbed during oxide reduction, the powder cooling in the plant, at storage in the air. Desorption temperature range is determined. Thermograms of powder oxidation testifying to a multistep character of the process are obtained. An increased tendency to oxidation of high-dispersity powders as compared to standard ones is noticed. An increased reactivity of high-dispersity powders is explained by considerable surface and crystal structure peculiarities