The heat exchanger is the main component of your furnace. If the heat exchanger has a crack or a rust hole, combustion fumes (including carbon monoxide) can contaminate the air in your home. This is a potentially deadly situation and should be addressed IMMEDIATELY. A cracked heat exchanger usually requires replacing the entire furnace. If you suspect that you might have a cracked heat exchanger, or a carbon monoxide problem caused by your furnace, turn the system off immediately. Then call us right away for service.