During a CAST, what is the primary purpose of analyzing flue gas?

Analyzing flue gas during a combustion appliance safety test is primarily focused on checking the efficiency and safety of the combustion process. The flue gas contains important information about how well the appliance is operating, indicating whether the combustion is complete and whether harmful byproducts, like carbon monoxide, are present. This analysis helps determine if the appliance is burning fuel efficiently and safely, adding vital information about the functioning and potential hazards of the appliance.

By measuring the levels of different gases in the flue, such as carbon dioxide, oxygen, and carbon monoxide, technicians can assess combustion performance and ensure that the appliance is operating within safe limits. High levels of carbon monoxide, for example, indicate incomplete combustion, which poses a safety risk to users. Thus, the analysis of flue gas directly contributes to evaluating both operational efficiency and safety, making it a crucial part of the CAST.