A furnace is often a background player for your home, keeping you warm during the cold winter months. It often won't be noticed until something breaks down. 

One cause may be that your furnace has a cracked heat exchanger. It can potentially be hazardous, so it’s worthwhile to know the evidence of a cracked heat exchanger and what you can do if you suspect that might be the problem.  

What Is a Heat Exchanger in a Furnace? 

A heat exchanger helps move heat from the combustion chamber of your furnace to the air that moves inside the air ducts. It typically does this via coils or tubes that heat the air while acting as a barrier to keep the gasses produced in the combustion chamber, called flue gasses, from leaking out into your home.  

Is a Cracked Heat Exchanger Dangerous? 

Thanks to its important role, it shouldn't come as a surprise that a broken heat exchanger can pose a risk. Cracks in the heat exchanger can allow dangerous gasses – including carbon monoxide, which can be lethal – to be distributed across your home. 

For this reason, don't ever turn on your heating if you think you're dealing with a cracked heat exchanger, as this could make the whole household sick. Call an HVAC professional right away if you think your heating has a cracked heat exchanger that needs to be repaired. 

Four Signs of a Cracked Heat Exchanger: 

  • Furnace turns off: A cracked heat exchanger can cause your furnace to shut off. 
  • Strange Smells: If the air leaving your furnace has an intense chemical odor, it could be evidence gas is leaking 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 poisoning symptoms: If a cracked heat exchanger is relieving carbon monoxide inside your home, your carbon monoxide alarm should go off or family members may struggle with signs of carbon monoxide poisoning. Complications include headaches, dizziness, weakness, nausea, vomiting or feeling drowsy. If the alarm goes off or you feel sick, exit the home right away and then call for help. 
  • Soot: If you spot black sooty collecting on the exterior of your furnace, it’s another sign something may be seriously wrong.

What to Do if a Furnace Heat Exchanger is Cracked 

If you worry your furnace has a cracked heat exchanger, hire a professional well versed in furnace installation The Bay Area right away so they can examine your system and, if needed, start a furnace heat exchanger replacement. Costs should fluctuate depending on the situation, but estimates can roughly suggest $1,000 to $3,000. 

However, the good news is that heat exchangers are regularly included in the warranty. You’ll want to review the warranty paperwork on your furnace, since while the warranty won't always cover the entire cost of repairs, it can significantly reduce your bill.  

How to Avoid a Cracked Heat Exchanger in Your Home  

One of the most convenient ways to avoid problems in your furnace overall is with routine furnace maintenance. Furnaces work the best when they run efficiently. Calling a trained professional to inspect your furnace for old parts, clogs in the air filters and other potential problems can keep you from getting a big bill later on.  

It’s also a good idea to take a look at your furnace filters every few months – it’s encouraged some filters be replaced every 90 days or sooner if they are dirty or grimy. While the filters are not part of the heat exchanger itself, the strain of drawing air through a clogged filter makes the entire furnace work more vigorously to do its job. And the harder your furnace has to work, the more deterioration parts like the heat exchanger will endure.