In a high vacuum particle wall, collisions occur much more frequently than in mutual elastic ones, therefore, chaotization (Maxwellization) does not take place. Hence, the gas‐phase state is determined by boundary conditions, i.e., surface scattering processes. In this paper, steady‐state equations of low‐density (molecular regime) gas, based on probability distribution functions of adsorption, desorption, and reflection, have been derived. Calculations performed for spherical and planar symmetry show that rarefied gas can be strongly nonuniform and anisotropic; deviations from homogeneity can reach one order of magnitude. The idea of experimental verification has been proposed. off