What are combustion products from fuel burning appliances plus excess air called?

Flue gases are the correct term for the mixture of combustion products released from fuel-burning appliances along with the excess air that is present during the combustion process. During combustion, fuels such as gas, oil, or wood undergo chemical reactions that produce various by-products, including carbon dioxide, water vapor, carbon monoxide, and other compounds, which are then carried away through the flue or chimney.

The presence of excess air during combustion helps to ensure complete burning of the fuel, reducing the likelihood of harmful emissions such as carbon monoxide. The gases created, along with the extra oxygen from the excess air, are collectively referred to as flue gases. These gases are typically vented outside the building to prevent dangerous accumulation indoors.

While exhaust gases, combustion gases, and venting gases also describe various aspects of the by-products of fuel combustion, 'flue gases' specifically refers to that combination released through the chimney or venting system, distinguishing it from more generalized terminology. Understanding these terms is essential for chimney sweeps and anyone involved in the installation or maintenance of combustion appliances, as it relates directly to safety and efficiency in venting systems.