The report documents briefly the fundamental mechanisms and limiting factors involved in electrostatic precipitation. It also discusses theories and procedures used in a model to describe the physical mechanisms. It generally describes the major operations performed in a computer program, lists the entire computer program, and defines all variables used in the program. Improvements in the model include a new way to calculate solutions to the electric field equations, a dynamic way to describe the effects of rapping reentrainment, a way to calculate effluent opacity, and a way to check the input data. Revision 3 of the model calculates efficiency in about 10% of the time required by Revision 1. The option to use input data expressed entirely in the metric system is provided, as are options to terminate the calculation after calculating V-I curves and to use an internal data set to estimate precipitator efficiency based on the resistivity of the dust particles. Computer program subroutines that perform fundamental calculations or utilize numerical techniques are described in sufficient detail to provide an understanding of their content and usage. A detailed flow chart is provided for each subroutine. Input and output variables are described, and limitations on these variables are noted.