A furnace is almost always a background player at home, helping keep you warm in the cold winter months. It regularly isn't noticed until a malfunction appears. 

One cause could be that your furnace has a cracked heat exchanger. It’s a potentially dangerous issue, so it’s worthwhile to familiarize yourself with the signs of a cracked heat exchanger and what to 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 inside your furnace to the air that moves throughout the air ducts. It typically accomplishes this with coils or tubes that heat the air while serving as a barrier to keep byproducts created 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 isn't surprising that a cracked heat exchanger can pose a risk. A damaged heat exchanger can permit dangerous gasses – like carbon monoxide, which can be lethal – to be distributed through your home. 

For that reason, do NOT use your heater if you suspect there's a crack in the heat exchanger, as this could make your entire household ill. Call an HVAC professional immediately if you believe your heating has a cracked heat exchanger that should be repaired. 

Four Symptoms of a Cracked Heat Exchanger: 

  • Furnace switches off: Cracks in the heat exchanger can cause your furnace to shut off. 
  • Strange Smells: If the air leaving your furnace has an intense chemical scent, it could be evidence gas is slipping through cracks in your heat exchanger. These byproducts, which may smell like formaldehyde, are a major warning sign. 
  • Carbon monoxide alarm is triggered or you recognize poisoning symptoms: If a cracked heat exchanger is emitting carbon monoxide in your home, your carbon monoxide alarm may go off or household members may struggle with signs of carbon monoxide poisoning. Side effects include headaches, dizziness, weakness, nausea, vomiting or feeling drowsy. If the alarm goes off or you feel unwell, leave the home as soon as you can and then call for help. 
  • Soot: If you notice black sooty collecting on the exterior of your furnace, it’s more evidence something could be seriously wrong.

What to Do if a Furnace Heat Exchanger is Cracked 

If you believe your furnace has a cracked heat exchanger, contact a professional with extensive experience in furnace installation Long Island right away so they can inspect your system and, if needed, handle a furnace heat exchanger replacement. Costs should differ depending on the situation, but estimates run in the neighborhood of $1,000 to $3,000. 

Estimates aside, the good news is that heat exchangers are often included in the warranty. You’ll want to check the warranty paperwork on your furnace, because while the warranty may not cover the entire cost of repairs, it still may significantly lower your bill.  

How to Prevent a Cracked Heat Exchanger in Your Home  

One of the easiest ways to minimize the risk of problems in your furnace overall is through routine furnace maintenance. Furnaces offer the most benefits when they operate efficiently. Calling a certified professional to inspect your furnace for worn-out parts, dirty filters and other potential problems can keep you from getting a big bill later on.  

It’s also helpful to review your furnace filters every few months – it’s encouraged some filters be swapped out every 90 days or sooner if they are dirty or grimy. While the filters aren't connected to the heat exchanger itself, the strain of pulling air through a clogged filter makes your entire furnace work harder to do its job. And the harder your furnace works, the more wear and tear parts like the heat exchanger will experience.