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

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

What Is a Heat Exchanger in a Furnace? 

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

Is a Cracked Heat Exchanger Dangerous? 

Given its key role, it’s no surprise that a broken heat exchanger can be hazardous. A damaged heat exchanger can enable dangerous gasses – including carbon monoxide, which can be lethal – to circulate through your home. 

For obvious reasons, don't ever use your furnace if you think it has a cracked heat exchanger, as letting it run could make the whole household sick. Contact an HVAC professional as soon as possible if you believe your heater has a cracked heat exchanger that needs repair. 

Four Warning Signs of a Cracked Heat Exchanger: 

  • Furnace shuts off: Cracks in the heat exchanger may cause your furnace to turn off. 
  • Unusual Smells: If the air escaping your furnace has a strong chemical scent, it could be a sign gas is seeping through cracks in your heat exchanger. These gasses, which can smell like formaldehyde, are a common warning sign. 
  • Carbon monoxide alarm initiates or you notice symptoms of poisoning: If a cracked heat exchanger is relieving carbon monoxide inside your home, your carbon monoxide alarm may 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, get out of the home right away and then call for help. 
  • Soot: If you notice black sooty buildup near the exterior of your furnace, it’s more evidence something may be seriously wrong.

What You Can Do if the Furnace Heat Exchanger is Cracked 

If you worry your furnace has a cracked heat exchanger, call a pro well versed in furnace installation Holdrege right away so they can examine your system and, if necessary, perform a furnace heat exchanger replacement. Costs often vary depending on the situation, but estimates run in the neighborhood of $1,000 to $3,000. 

Fortunately, the good news is that heat exchangers are generally included in the warranty. You should review the warranty paperwork on your furnace, since while the warranty might not cover the entire cost of repairs, it still may significantly lower your bill.  

How to Avoid a Cracked Heat Exchanger in Your Home  

One of the best ways to avoid problems in your furnace overall is with regular furnace maintenance. Furnaces work the best when they work efficiently. Hiring a skilled professional to examine your furnace for worn-out parts, dirty filters and other common problems can help you avoid getting a big bill later on.  

It’s also beneficial to review 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 aren't a part of the heat exchanger itself, the strain of drawing air through a clogged filter makes the entire furnace work more vigorously to accomplish its job. And the harder your furnace needs to run, the more deterioration components like the heat exchanger will experience.