The physical and mathematical models of heat and mass exchange are given for the process when gas bubbles become saturated with liquid vapors in bubbling of a gas through this liquid. A basic task of simulation is to determine a time dependence of volume concentration of liquid vapors in the gas-vapor mixture at the outlet of the bubbling device. The created calculation technique is tried out in designing and testing of the bubbling device for making the benzene-air mixture used in the laboratory setup intended for trapping benzene vapors at the petrol station. The calculated and experimental data are compared and analyzed.