Analysis of initial and boundary conditions for convective diffusion of vapors and aerosols in closed volumes

The publication describes mathematical modeling of environmental assessment after the selection of toxic chemicals. An assessment is made of the ecological state of enclosed spaces after the release of toxins was conducted. Two methods are considered: the field of instantaneous concentration of a chemical substance and the field of integral concentrations of a chemical substance of convectivediffusion (convention) and (diffusion) processes. The mathematical instrument of methods is described. The essence of the method based on instantaneous concentration fields of a chemical substance is the compilation of differential equations of the first order of the material balance, with the control of the decrease of the substance in a short time. The essence of the convective-diffusive (convention) and (diffusion) processes is described-these are second-order parabolic partial differential equations. Tables with classifications of source types and ciphers are presented. The variants of the accident scenario are described. Calculated fields of instantaneous concentrations of chemicals in the coordinates. In modeling, exposure is used. Finite series obtained. The initialization and boundary conditions are formalized. Analytical and numerical methods are proposed for calculating the fields of instantaneous concentrations of chemicals and exposure doses of toxic substances in enclosed spaces. It is proposed to consider mathematical tools for determining the concentration of COVID-19 infection in enclosed spaces