Abstract <p>Charging of micrometer-sized dust particles in multicomponent plasma of humid air and H₂O‒O₂–N₂ gas mixtures at different gas ionization rates by an outer ionization source has been considered. The charge of dust particles is determined based on the kinetic model of ion-molecular processes, which includes more than 600 reactions for electrons, negative and positive ions, including hydrated ions containing up to twelve water molecules. It was found that despite the negligible electron density far from a dust particle in an undisturbed plasma, the charge of dust particles in humid air when the gas ionization rate exceeds the critical value is determined precisely by the electron flux. This leads to sufficiently high dust particle charge comparable with the charge in electropositive gases. The influence of the gas ionization rate and its composition on the dust particle charge is studied. A comparative analysis of the obtained data with the results of the analytical theory of particle charging at elevated pressures is carried out. The issue of the influence of the particle charge polarization under the action of a point charge of an ion (electron) on the charge of dust particles is considered.</p>