What is considered a good percentage of CO2 in flue gas analysis?

In flue gas analysis, a CO2 concentration between 12% and 15% is generally considered optimal for achieving efficient combustion and indicating that the combustion process is functioning effectively. This range suggests that the air-to-fuel ratio is well-balanced, meaning there is enough oxygen for combustion without excessive amounts, which could lead to wasted fuel and lower efficiency.

When CO2 levels are within this range, it reflects that the fuel is being burned cleanly, translating to higher energy output and lower emissions of harmful pollutants. Additionally, this level typically indicates that the system is operating at a higher efficiency, contributing to energy savings and improved environmental compliance.

Higher levels of CO2 can suggest complete combustion, but if the concentration is too high, it may also point to other issues such as improper air supply or fuel excess. Conversely, lower levels, such as those found in the other options, indicate incomplete combustion or inefficiencies that need to be addressed to optimize performance and reduce emissions.