Carbon Monoxide and Heat Exchangers

November 02, 2018

Carbon monoxide, the poisonous, colorless, odorless and tasteless gas responsible for more than 20,000 visits to the emergency room every year, can pose a danger from unexpected sources in your home, including fireplaces.

Factual information about carbon monoxide 

What is a heat exchanger and why is it critical?
A furnace's heat exchanger is a metal component that transfers heat from the fuel being burned while blocking the air in your home from mixing with the furnace exhaust. Sometimes the heat exchanger fails, either from cracks generated by constant expansion and contraction due to heating and cooling of the metal, or from rust. When a heat exchanger fails—under specific conditions—the exhaust gases, including carbon monoxide, can combine with the air in the house. A properly running furnace should not produce significant levels of carbon monoxide; however, a cracked or leaking heat exchanger can present a safety hazard.

What are the hazards correlated with a cracked heat exchanger?
A cracked heat exchanger could allow exhaust gas from the furnace to contaminate the household air with exhaust gases including carbon monoxide. In order for this to happen, the furnace must be emitting high levels of carbon monoxide and the exhaust gas must be combining with the household air. This could lead to serious illness and even death.

What are the warnings of a cracked heat exchanger?

In addition to a visual inspection to diagnose a crack, there are a few warnings of a potential issue with your heat exchanger that you may observe. If you turn the heat on and the flames flicker and appear devilish, this could be a clue that circulated air from the furnace is getting into the combustion area and you should have it inspected by an HVAC technician. Although you certainly hope it doesn’t reach this point, other signals of trouble include carbon monoxide detectors sounding and you or your family members feeling sick, lightheaded or nauseous. To ensure the safety of all occupants, all homes should have a operational carbon monoxide detector and batteries should be replaced regularly.

How can I be certain that my heat exchanger really has failed?
Service Experts’ ACE-certified technicians have received specialized training in identifying a cracked heat exchanger. As standard practice and in addition to physically observing the presence of a hole or crack, cameras are used. Whenever possible, the technician will show customers the failed heat exchanger—or at least a photo of it—so they can see for themselves. Additionally, an expert technician will test both the home and furnace for carbon monoxide. A properly functioning furnace should not generate significant levels of carbon monoxide. The technician will then warn the customers of the dangers associated with the failed part and give professional guidance regarding next steps.

What happens after an HVAC technician confirms a cracked heat exchanger?
Once you have a confirmed diagnosis from an expert, your firstquestion will likely be whether the part can be repaired or if replacement is the only option. Unfortunately, industry standard is that the heat exchanger must be replaced. In fact, the American Gas Association recommends that any visible crack or hole is reason for requiring replacement of the heat exchanger or furnace.

 Common household appliances that release carbon monoxide

If my heat exchanger has failed, do I have to replace the furnace?
While it may end up making sense to replace the furnace rather than only the heat exchanger, that is not always the case. Furnace warranties can vary—most furnaces have a 10-year warranty on the heat exchanger, while some are covered for 20 years or even for the life of the furnace. Our technicians will help you investigate the warranty on your heat exchanger and provide all the information you need to decide if replacing the heat exchanger or the entire furnace is right for you.


Service Experts Heating & Air Conditioning suggests changing your carbon monoxide detectors every five years and checking your carbon monoxide detectors every month to make sure the batteries and alarm are working effectively. And by keeping up with the normal maintenance of your equipment, you will have peace of mind knowing that it’s going to be safe. If you suspect a problem with your heat exchanger or need to have an analysis of carbon monoxide levels in your home, call Aramendia Plumbing, Heating and Air today at 210-404-4233 or schedule an appointment online.

Tips for keeping the home safe from carbon monoxide