What is the purpose of the heat exchanger in a forced warm-air furnace?

The heat exchanger in a forced warm-air furnace serves the crucial function of transferring heat from combustion gases to the air that is circulated throughout a building. In the operation of a furnace, fuel is burned to create hot gases. The heat exchanger allows this heat to be transferred to the air before it travels through the ductwork into living spaces.

This transfer is vital for maintaining indoor comfort while ensuring that harmful combustion gases, such as carbon monoxide, are safely vented outside rather than being circulated into the living area. The design of the heat exchanger facilitates the efficient transfer of heat while keeping the combustion gases separate from the air that will be breathed by occupants. This separation is essential for safety and effective heating.

The other options mention functions that are not the primary role of a heat exchanger in this context. Mixing fresh and exhaust air, filtering air contaminants, and creating warm air pressure do not accurately describe what the heat exchanger specifically does in a forced warm-air furnace system.