The Integrated Air Pollution Control System (IAPCS) was developed to estimate costs and performance for emission control systems applied to coal-fired utility boilers. The model can project a material balance, equipment list, capital investment and revenue requirements based on user- specific input data. Included in the model are conventional and emerging technologies affecting SO2, NOx, and particulate matter pre-combustion, in-situ, and post-combustion emission controls. A variety of technology modules built into the model can be incorporated and combined. Cost and performance estimates can be analyzed in terms of integrated technologies. Conventional and emerging technologies included in IAPCS Version 4.0 are overfire air/low NOx burners, lime injection multistage burners, physical coal cleaning, coal switching and blending, spray humidification, electrostatic precipitator, fabric filter, lime spray drying, wet limestone flue gas desulfurization, dry sorbent injection, natural gas reburning, selective catalytic reduction, atmospheric fluidized bed combustion, pressurized fluidized bed combustion, integrated gasification combined cycle, and pulverized coal burning boiler. The model generates capital, annualized, and unitized pollutant removal costs in either constant or current dollars for any year.