The heat exchanger is the part of the furnace where the combustion process takes place. The heat exchanger is made of various types of metal depending on the manufacturer.
Most furnaces have a heat exchanger that consists of two or more individual sections or tubes.
Poor maintenance can shorten the life of a heat exchanger. During the expansion and contraction of the heat exchanger during the heating process, sections can open up at the seams or split open at a weak spot and could allow dispersal of the combustion gases into the air stream going to your living space. Please refer to the next two questions for more information on carbon monoxide. A. Carbon monoxide is produced during incomplete combustion of fuels such as natural gas, LP, wood, oil, etc. As we make our homes more air tight, we reduce the required air supply to the fuel burning appliances, thus causing incomplete combustion.