Don’t panic just yet. Furnaces are not inherently dangerous, and often you have nothing to fret about. However, it is important to be aware that systems combusting natural gas have the potential to create health hazards if improperly maintained and repaired. That being said, the best way to avoid a dangerous situation is to schedule regular maintenance.
The dangerous furnace malfunction we are referring to is a cracked heat exchanger. The heat exchanger is the part of a natural gas furnace where the heat from the combustion gas transfers to the air from the blower fan that moves into the ventilation system. To put it simply, the heat exchanger is the part that actually heats the air. Once the heating process is finished, the combustion byproducts in the heat exchanger are vented out of the system through a flue to release the gas harmlessly into the air.