When venting spillage occurs and flue gases pass back through combustion zones, what change occurs?

When venting spillage occurs and flue gases are allowed to pass back through the combustion zones, there is a change in the chemical composition of those gases. Specifically, the increased presence of flue gases being recirculated through these combustion zones can lead to the reduction of carbon dioxide (CO2) back to carbon monoxide (CO). This happens primarily due to incomplete combustion or insufficient oxygen availability for the combustion process to occur fully.

The combustion process ideally results in carbon burning to produce CO2. However, if combustion is interrupted or not fully efficient—such as during spillage where gases might backtrack—the environment can become more reducing, allowing for the conversion from CO2 to CO. This change implies that instead of efficiently venting away as less harmful exhaust, instead, harmful levels of CO can be produced, which poses significant safety risks.

Understanding this process is vital for ensuring the safety and efficiency of heating systems, as excessive CO is toxic and presents serious hazards.