A furnace is often a background player in your home, keeping you warm across the cold winter months. It frequently isn't noticed until a malfunction appears. 

One root cause might be that your furnace has a cracked heat exchanger. It can potentially be hazardous, so it’s worthwhile to learn the symptoms of a cracked heat exchanger and what you should do if you believe that is the problem.  

What Is a Heat Exchanger in a Furnace? 

A heat exchanger transfers heat from the combustion chamber in your furnace to the air that circulates inside the air ducts. It generally handles this using coils or tubes that warm the air while serving as a barrier to keep gas produced in the combustion chamber, called flue gasses, from escaping out into your home.  

Is a Cracked Heat Exchanger Dangerous? 

Because of its key role, it shouldn't come as a surprise that a broken heat exchanger can be very dangerous. Cracks in the heat exchanger can allow dangerous gasses – such as carbon monoxide, which can be lethal – to flow across your home. 

For that reason, don't ever run your furnace if you believe it has a cracked heat exchanger, as this could make your entire household sick. Reach out to an HVAC professional immediately if you believe your heater has a cracked heat exchanger that should be repaired. 

Four Signs of a Cracked Heat Exchanger: 

  • Furnace shuts off: A crack in your heat exchanger could cause your furnace to turn off. 
  • Unusual Smells: If the air leaving your furnace has a strong chemical smell, it may be evidence gasses are slipping through cracks in your heat exchanger. These gasses, which may smell like formaldehyde, are a major warning sign. 
  • Carbon monoxide alarm initiates or you notice health problems: If a cracked heat exchanger is releasing carbon monoxide inside your home, your carbon monoxide alarm could go off or family members may struggle with signs of carbon monoxide poisoning. Complications include headaches, dizziness, weakness, nausea, vomiting or feeling tired. If your alarm goes off or you feel sick, exit the home immediately and then call for help. 
  • Soot: If you see black sooty buildup around the exterior of your furnace, it’s more evidence something might be seriously wrong.

What You Should Do if the Furnace Heat Exchanger is Cracked 

If you suspect your furnace has a cracked heat exchange