Boundary-value problem of radiation transfer in optically thick layers is considered while describing ocean, cloudiness, aerosol particle outbreaks, dust traces and other specific effects resulted from large fires (forest, peat-lands, in steppe regions, anthropogenic). Space and angular distributions of radiation inside the relevant layer of these media as well as reflected and passed through the layer radiation are formed as a result of multiple scattering and absorption. A new approach has been proposed to radiation transfer modeling in thick layers based on an influence function method. An internal border is inferred that separates the relevant layer on two regions. The influence function is calculated in the first region as a complete solution of the planar problem and as an asymptotic solution in the second region considering both cases of this last solution as that of a azimuth symmetric problem or as a complete solution of kinetic equation. The total radiation in the layer and outside it is found by a matrix functional known as the optical transfer operator the nuclei of which are given by the influence functions for each region. Forward and back hemispheres of the phase function serve as reflection and extinction coefficients of the internal border