The air coming out of a chimney after combustion in the burner it is venting. It can include nitrogen oxides, carbon oxides, water vapor, sulfur oxides, particles and many chemical pollutants.
Source:
US Environmental Protection Agency
Glossary
Carbon dioxide (CO2) - Nitrogen oxides (NOx) - Particulate matter - Sulphur dioxide (SO2)
Español: Gas de combustión
Français: Gaz de combustion
Nederlands: Rookgas