What does an elevated CO2 reading in flue gases typically indicate?

An elevated CO2 reading in flue gases is a strong indicator of improper combustion conditions. When combustion is functioning correctly, the gases produced will have a specific balance of constituents, including byproducts such as CO2, CO (carbon monoxide), and unburnt hydrocarbons. A high level of CO2 suggests that the combustion process is not optimizing the air-fuel mixture, possibly due to issues like a lack of adequate air, leading to incomplete combustion.

In a properly adjusted burner, there should be enough oxygen available to ensure that the combustion process converts the fuel completely into CO2 and water vapor. If there is a deficiency in oxygen or if the combustion is occurring inefficiently, this can result in an excess of CO2 along with other harmful byproducts, potentially exposing the system and its users to increased safety risks.

Each of the other options relates to combustion conditions, but they do not directly indicate the elevated CO2 situation as clearly as improper combustion conditions. High oxygen levels, for example, would not be a typical cause of high CO2 and instead signify a different imbalance. Normal operating conditions should exhibit a consistent and expected range for CO2 and other gases, while low gas pressure may lead to poor combustion efficiency but not necessarily an elevated CO2