The area source model of particulates was deeply researched, and the places of the initial precipitation of the area sources of particulates were determined. The precipitation of the particulates into the inside of the area source would not be considered. The concentration of the particulates in the inside of the area source block equalled the source intensity of the pollutants of the unit area that was multiplied by the reflection coefficient of the ground surface and divided by the wind speed of the ground surface.

The particulate precipitation of the outside of the area source would be considered. Using the back set method of the virtual point source, and referring to the tilt smoke and cloud model of the part reflex of the point source, the area source model of the particulates was fully given. The edge concentration of the area source was processed by the part of the linear insertion, lest the discontinuity of the calculated results. The central point place of the area sources should be moved horizontally a micro-distance at X and Y directions so that the possibility of the coincidence of both the calculated point and the central point of the area sources would be eliminated.