What does the term 'flue gas' refer to?

The term 'flue gas' specifically refers to the exhaust gases that are produced as a byproduct of combustion within a boiler. When fuel is burned in the boiler, it generates heat that converts water into steam. This combustion process produces gases, including carbon dioxide, nitrogen oxides, and other byproducts, which are collectively termed flue gases. These gases must be vented safely out of the boiler to prevent the accumulation of harmful substances and ensure efficient operation of the heating system. Proper management and monitoring of flue gases are crucial for both efficiency and safety in boiler operation.

The other options address different aspects of boiler operation. Steam produced by a boiler is the desired output for heating processes, while condensate refers to the water that forms when steam cools and condenses back into liquid form. The air entering the combustion chamber is necessary for combustion but does not represent exhaust gases; instead, it is a component of the combustion process itself. Understanding the role and implications of flue gas is essential for effective boiler operation and maintenance.