Can a New Furnace Make You Sick? 3 Ways It Can and How You Can Fix It


It is natural to assume that an old furnace is more likely to endanger your health than a brand new heating system would. So homeowners give in to replace their furnace of many years at the slightest suggestion that it could cause them various illnesses. Anyway, “New is always better,” right? Not always. Can a new furnace make you sick?

Any furnace, old or new, can cause health problems if not properly maintained. Lack of regular maintenance by a licensed expert can cause some, if not all, of the following:

  • The build-up of dust, pollen, and other dirt in the air filters and ductwork triggers allergy symptoms
  • Unresolved heat exchanger problems cause carbon monoxide poisoning
  • Insufficient moisture in the air leads to dry throat and nasal passages and skin irritations
can a new furnace make you sick

You were thrilled to get your shiny new furnace in the hope of protecting your family from the harsh winters. But after some time, instead of giving you your expected warmth and comfort, your new high end variable speed furnace seems to make you sneeze, cough, and cause you to have itchy eyes and sore throat as soon as it is turned on.

You wonder, “Did we waste all that money to replace our trusty old furnace if a new one is making us sick anyway?”

It may not be easy to hear the whole truth but it is better to be safe than sorry. Let’s find out first how your old furnace could be making you sick and why your new furnace is not all that different.

Dust Doesn’t Discriminate

Because huge old furnaces are usually hidden away in basements or garages, it might be easy to forget to clean them regularly. And if the furnace seems to still do a good job of heating your home, you may not be bothered about the years’ worth of dust gathering inside there. 

But it only takes a few months for furnace filters to accumulate dirt that can hinder the heating system’s efficiency.  So regardless of whether your furnace is old or brand new, dust, pollen, and other dirt buildups can still jeopardize the quality of your indoor air quality.

Worse, you could be housing dust mites, tiny insects that thrive in dusty and humid places, inside your furnace that can prompt many undesirable symptoms:

  • Sneezing
  • Coughing or wheezing
  • Red, watery, and itchy eyes
  • Scratchy throat
  • Stuffy or runny nose
  • Difficulty in breathing

What You Can Do

No matter how old your furnace is, be sure to consistently free it from dust and other dirt, like the dangerous mold growth. Especially, if your heating system has been dormant all through spring and summer, make sure to give it a good clean before turning it on in the winter.

Truth be told, air filters’ main role is to sift out harmful particulates that can damage the internal components of your furnace. A happy coincidence is that they also block allergens and pollutants from spreading over your breathing space. 

So by cleaning and maintenance you are not just sparing your family from health risks but also saving yourself from pricy repair costs.

It’s highly recommended to have your furnace cleaned by a professional every year. And have your ductwork evaluated for cleaning every 5-7 years.

Carbon Monoxide Can Be Fatal

Old or new, a natural gas furnace is one of the many home appliances that commonly emit carbon monoxide (CO) because of its fuel-burning feature.

In normal circumstances, CO is contained within the heat exchanger and will be released safely from your home via the furnace flue pipe. In a handful of very dangerous occasions, the heat exchanger may crack and let out CO inside your home. 

The US Environmental Protection Agency (EPA) in agreement with other authorities on energy use and safety recommends 9 parts per million (ppm) of CO for an indoor setting for no more than 8 hours. At 35 ppm, exposure to CO after 6 to 8 hours can cause undesirable symptoms such as:

  • Headache
  • Fatigue
  • Nausea
  • Confusion
  • Vomiting

If the CO levels reach 200 ppm to 400 ppm, you are already experiencing severe carbon monoxide poisoning with the following effects depending on the length of exposure:

  • Angina or intense chest pain due to reduced blood supply
  • Dyspnea or feeling of suffocation
  • Seizures
  • Comatose
  • Death

What You Can Do

No less than 430 people die each year from carbon monoxide poisoning, while 50,000 are taken to emergency rooms due to accidental exposure to CO. Because it is invisible to the eyes and odorless, CO could be your family’s most fatal enemy.

But CO poisoning is highly preventable with a few easy steps. Surprisingly, it does not depend on whether your furnace is 1 year or 15 years old.

  1. Install carbon monoxide detectors on every floor of your house, including the basements and the attic.
  2. CO monitors should be at least 5 feet above the floor and placed near or right outside your bedroom. Replace the batteries and test their efficiency at least annually. 
  3. Even state-of-the-art furnaces are susceptible to a carbon monoxide leak if not regularly serviced and maintained by a qualified contractor. Be vigilant about increased rust formation on the pipes or spots forming around the furnace area.

Dangerously Low Humidity

Too much moisture in the air during summertime is so uncomfortable that it makes you feel ill. Who wants to feel icky and muggy with sweat, anyway?

But on the other extreme, low humidity can occur during cold seasons because the cold air can only carry a small amount of water in it, unlike warm air.

Because indoor air that has low humidity feels colder than air with a higher level of moisture, most people will crank up their heaters even higher in the hope to feel warmer but this will actually make matters worst.

The ugly effects of low indoor humidity include:

  • Dry skin
  • Dehydrated sinuses
  • Bloody nose
  • Parched and cracked lips
  • Sore throat
  • Itchy eyes

What You Can Do

It does not matter if your furnace is the latest model or it was purchased way back, the problem with low humidity can be resolved with the help of the following:

1. Use a humidifier, evaporator, or steam vaporizer. These will help maintain the indoor humidity to a safe level of between 30% to 50%. Anything above or below this percentage will cause unpleasant symptoms.

2. Like your furnace, regularly clean and maintain your humidifier to prevent mold and bacteria growth that would promote more illnesses.

3. Drink water to keep you hydrated, especially before sleeping. If your nasal airways are dry, try steam inhalation or nasal spray.


Regardless of how old or how new your heating system in place is, nothing can take the place of regular and proper maintenance of your furnace. A professional you can trust can diagnose seemingly trivial problems at first but can cost you your health if you ignore them.

Plus, minor furnace problems that can be detected and solved by routine checkups of a professional may turn into major breakdowns over time. A faulty furnace will fail to maintain good indoor air quality which can lead to serious health issues.

3 thoughts on “Can a New Furnace Make You Sick? 3 Ways It Can and How You Can Fix It”

  1. Old furnace was replaced with a new furnace due to the old one having a cracked heat exchanger, When the heat is now on I smell something like a solvent smell – smell is difficult to describe but wake up with dry, sore throat – even the dog wakes up experiencing difficulty swallowing, Concerned that solvent smell may be carcinogenic in some way.

    • Hi Daryl

      It’s hard to say what would be creating a solvent smell. Normally there’s not any leftover solvents used when manufacturing or installing a gas furnace. There can be some oil from manufacturing but that burns off within the first few times the furnace is used and any smell goes away. My biggest concern when you’re feeling a physical effect is carbon monoxide. Even a new gas furnace can make carbon monoxide. Make sure you have a carbon monoxide detector. Low levels of CO can show as the symptoms you’re describing so if you really want to be safe, I’d recommend a low level carbon monoxide detector like the one here: (NOT an affiliate link)

    • Dear Daryl,

      I had the same experience. My furnace had to be replaced in February because of a broken heat exchanger. When the furnace was initially started up, it filled my house with fumes and set off the fire alarms. The technicians said that always happens, and that it was because the new furnaces are coated with some sort of protectant. They said it would burn off within a day, but it took more than a month before the fumes and bad smell went away. I have read online that others have experienced this also. Hopefully all of your chemicals are burned off by now and that you and your dog are doing ok.


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