In a natural gas furnace with perfect combustion, what is the expected percentage of CO2 content in the flue gases?

In a natural gas furnace that utilizes perfect combustion, the theoretical combustion process primarily produces carbon dioxide (CO2) and water vapor (H2O) as byproducts. When natural gas, which largely consists of methane (CH4), is combusted completely, it reacts with the oxygen in the air to convert into CO2 and water.

Under ideal conditions, the CO2 content in the flue gases for such a combustion would typically fall within the range of 2% to 5.5%. This range reflects the efficient conversion of fuel, where a minimal portion of the gas remains unburned, and the nitrogen and other inert gases present in the combustion air do not contribute to carbon dioxide levels.

Outside of that range, lower CO2 content would indicate incomplete combustion, which could arise due to insufficient oxygen supply or improper function of the system. Higher values than 5.5% may suggest some inefficiencies or incomplete combustion, as excess carbon monoxide (CO) and other exhaust components would appear in flue gases, affecting the CO2 levels.

Hence, the expected CO2 content in the flue gases, when assuming perfect combustion in a natural gas furnace, is indeed situated in the range of 2% to 5