Flue gas treatment is a process designed to reduce the amount of pollutants emitted from the burning of fossil fuels at power plants. The pollutants may contain sulfur dioxide, mercury, and carbon dioxide. Most flue gas, however, consists of nitrogen oxides. If left untreated , flue gas from power plants can substantially affect local and regional air quality. Under many national-level clean -air regulations, power plants and other facilities are required to use flue gas treatments to reduce the amount of emitted pollutants. Flue gas ducting, housing, filters and chimneys are subject to particular chemical, abrasive and temperature requirements.