Flue gas is the
gas exiting to the atmosphere via a
flue, which is a pipe or channel for conveying exhaust gases from a fireplace, oven,
furnace,
boiler or
steam generator. Quite often, the flue gas refers to the
combustion exhaust gas produced at
power plants. Its composition depends on what is being burned, but it will usually consist of mostly
nitrogen (typically more than two-thirds) derived from the combustion of air,
carbon dioxide , and
water vapor as well as excess
oxygen (also derived from the combustion air). It further contains a small percentage of a number of pollutants, such as
particulate matter (like
soot),
carbon monoxide,
nitrogen oxides, and
sulfur oxides.