If a burner is set "rich", which element would NOT be found in the exhaust analysis?

When a burner is set to "rich," it indicates that there is an excess of fuel compared to the amount of air supplied for combustion. This results in incomplete combustion, which typically means that the combustion process is not achieving optimal efficiency.

In this situation, carbon dioxide (CO2) is produced to a certain extent, but instead of the expected complete oxidation, the combustion may also produce carbon monoxide (CO) and hydrogen (H2) due to the lack of sufficient oxygen. Consequently, the presence of hydrogen in the exhaust is likely, as it can be a product of incomplete combustion.

The high levels of carbon monoxide often indicate that there has not been enough oxygen to fully oxidize the fuel, resulting in unburned components as well. Oxygen (O2) is expected to be present in higher amounts than if the burner were set to a stoichiometric (ideal) setting, as there would be residual oxygen from the incomplete combustion of the fuel.

Nitrogen (N2) is typically found in the exhaust as well, as it is a primary component of air and remains unchanged during combustion. Therefore, it will always be present in the exhaust regardless of the burner setting.

Given this context, carbon dioxide (CO2) would be present