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

One source could be that your furnace has a cracked heat exchanger. It can potentially be hazardous, so it’s worthwhile to familiarize yourself with the symptoms of a cracked heat exchanger and what you should do if you are worried that may be the problem.  

What Is a Heat Exchanger in a Furnace? 

A heat exchanger transfers heat from the combustion chamber inside your furnace to the air that flows inside the ventilation. It usually handles this through coils or tubes that warm the air while functioning as a barrier to keep byproducts formed in the combustion chamber, called flue gasses, from leaking out into your home.  

Is a Cracked Heat Exchanger Dangerous? 

Given its key role, it’s no surprise that a damaged heat exchanger can pose a risk. A crack in the heat exchanger can enable dangerous gasses – such as carbon monoxide, which can be lethal – to be distributed throughout your home. 

For obvious reasons, don't ever run your furnace if you think there's a crack in the heat exchanger, as doing so could make the whole family sick. Contact an HVAC professional as soon as possible if you think your furnace has a cracked heat exchanger that needs to be repaired. 

Four Warning Signs of a Cracked Heat Exchanger: 

  • Furnace turns off: A crack in your heat exchanger may cause your furnace to switch off. 
  • Strange Smells: If the air escaping your furnace has a powerful chemical smell, it might be evidence gasses are slipping through cracks in your heat exchanger. These byproducts, which can smell like formaldehyde, are a major warning sign. 
  • Carbon monoxide alarm is triggered or you recognize symptoms of poisoning: If a cracked heat exchanger is relieving carbon monoxide inside your home, your carbon monoxide alarm could go off or household members may start experiencing signs of carbon monoxide poisoning. Symptoms include headaches, dizziness, weakness, nausea, vomiting or feeling tired. If the alarm goes off or you feel unwell, exit the home right away and then call for help. 
  • Soot: If you see black sooty accumulating around the exterior of your furnace, it’s an indication something could be seriously wrong.

What You Can Do if Your Furnace Heat Exchanger is Cracked 

If you believe your furnace has a cracked heat exchanger, hire a pro well versed in furnace installation Athol as soon as possible so they can examine your system and, if necessary, start a furnace heat exchanger replacement. Costs will differ depending on the situation, but estimates often hover around $1,000 to $3,000. 

However, the good news is that heat exchangers are often included in the warranty. It's a good idea to confirm the warranty paperwork on your furnace, since while the warranty won't always cover the entire cost of repairs, it still may significantly reduce your bill.  

How to Avoid a Cracked Heat Exchanger in Your Home  

One of the easiest ways to avoid problems in your furnace overall is with routine furnace maintenance. Furnaces work the best when they work efficiently. Contacting a skilled professional to check your furnace for worn-out parts, clogs in the air filters and other likely 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 changed 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 drawing air through a clogged filter makes your entire furnace work harder to complete its job. And the harder your furnace needs to run, the more strain parts like the heat exchanger will sustain.