What gases are typically measured in flue gas analysis and why?

• A. Oxygen (O2), carbon dioxide (CO2), carbon monoxide (CO); sometimes NOx and unburned hydrocarbons; to assess combustion efficiency and emissions.
• B. Hydrogen, helium, neon; to measure fuel quality.
• C. Argon, methane; to calibrate sensors.
• D. Sulfur dioxide only; to monitor acidity.

Answer: (A)