carbon monoxide furnace

Carbon monoxide is an odorless, colorless gas that can’t be detected by human senses. It’s a byproduct of the incomplete combustion of fuels and can be produced by large home appliances like water heaters, gas stoves, or furnaces and boilers. Small amounts of carbon monoxide generally filter harmlessly out of the home, but an accumulation of the gas can have serious consequences. If there’s a chance you’re worried about a carbon monoxide furnace leak, keep reading to learn how to stay safe.

Because you can’t see or smell carbon monoxide, it’s important to check your home regularly for unsafe levels. A carbon monoxide alarm will alert you if the concentration in your home reaches an unsafe level, but a proactive approach is recommended.

In this guide, we’ll discuss how to determine if your furnace is leaking carbon monoxide and what to do if it is. We’ll also share how to prevent your furnace from leaking harmful levels of carbon monoxide.

Is My Furnace Leaking Carbon Monoxide?

When the temperature outside starts to drop, most people crank up the thermostat. When your furnace is running constantly it can produce a significant amount of carbon monoxide. Furnaces and boilers are designed to vent this harmful gas away from the home, but an old or poorly maintained furnace can develop a leak. According to the CDC, carbon monoxide is a silent killer that takes hundreds of lives per year.

Unfortunately, you can’t tell just by looking at your furnace whether it’s leaking carbon monoxide. You need a carbon monoxide detector or other special equipment to test the levels yourself. That being said, there are some signs and scenarios that might give you a clue.

Here are some of the signs that carbon monoxide could be accumulating:

  • Pilot light frequently blows out
  • Brown or yellow stains appear around the appliance
  • Smell of gas or exhaust
  • Fallen soot accumulating in the fireplace
  • Stale or stuffy air
  • Smell of something burning
  • Excessive condensation on windows around the furnace
  • Yellow burner flame rather than blue
  • Absence of upward draft in the chimney
  • Soot, smoke, or fumes coming from the chimney

The signs of carbon monoxide accumulation can be subtle, and it may take some time before you notice them. This is why it’s important to know the signs of accumulation AND the early signs of carbon monoxide poisoning.

Here are some of the symptoms of carbon monoxide poisoning:

  • Nausea
  • Weakness
  • Shortness of breath
  • Vomiting
  • Chest pain
  • Blurry vision
  • Dull headache
  • Dizziness
  • Blacking out
  • Confusion

The severity of symptoms will vary depending how long you’ve been exposed to carbon monoxide. In serious cases of prolonged exposure, brain damage and death are possible. If you suspect a carbon monoxide leak or experience symptoms of poisoning, get out of the house immediately and get help.

How to Tell if You Have a Carbon Monoxide Furnace Leak

If you have a gas furnace, carbon monoxide will be a concern – electric furnaces do not create carbon monoxide. Just because your furnace produces carbon monoxide, however, doesn’t necessarily mean it’s a hazard. When a furnace is properly maintained and vents well, carbon monoxide won’t accumulate to dangerous levels. If it’s very old or if you haven’t changed the filter or had the unit serviced in a while, however, the risk starts to increase.

The best way to confirm that your furnace is leaking carbon monoxide is to use an instrument specifically designed to test for toxic gases. You can hire a private company to conduct an indoor air quality test which includes carbon monoxide testing, or you can call an HVAC company out to service the unit. Testing for carbon monoxide is generally included in this service. HVAC companies have the equipment to test the gasses being vented directly from the furnace.

Another option is to purchase a consumer-level carbon monoxide detector. You simply set up the device near your furnace and it will alert you if carbon monoxide levels exceed a certain level. Most detectors only measure down to 30 ppm carbon monoxide, so they are best used as a last-level warning rather than a form of monitoring. Keep in mind as well that efficacy of the unit depends on placement – refer to the manufacturer’s instructions to make sure you set the unit up properly.

What to Do If Your Furnace is Leaking Carbon Monoxide

If you have reason to believe carbon monoxide is accumulating in your home, get out. It’s as simple as that. Turn off cooking appliances as well as your HVAC system and water heater then open the doors and windows as you leave to help vent the harmful gasses.

Once you’re safely out of the home, call the fire department or your gas company to come check the air quality with professional equipment. Even if the alarm shuts off before they arrive, do not assume it’s safe to reenter the home. Opening the doors and windows may diminish the level of carbon dioxide in the air, but the furnace could still be producing it.

Most importantly, do not ignore a carbon monoxide detector. If it goes off, assume that it’s working correctly and detecting unsafe levels of carbon monoxide in your home.

How to Prevent a Carbon Monoxide Furnace Leak

When it comes to a gas furnace, carbon monoxide leaks can develop for a number of reasons. A dirty filter can compromise airflow. A cracked heat exchanger or flue pipe can cause a leak. For these reasons, it’s essential that you change your filters regularly and have the unit serviced annually.

Here are some tips to prevent your furnace leaking carbon monoxide:

Make Sure the Furnace is Installed Properly

While you might be able to install certain furnace models yourself (and could save money by doing so), it’s generally not recommended. Not only could you void your warranty by forgoing professional installation, but you might not align the ductwork properly to ensure the carbon monoxide is vented correctly.

Change the Air Filter on Your Furnace Regularly

For 1-to-2-inch filters, replace every one to three months. For 3-to-4-inch filters, change every 6 to 9 months. If you have a smart thermostat, it may even remind you when the filter needs to be changed.

Have Your Furnace Serviced Once a Year

Annual maintenance may be the best way to prevent your furnace from leaking carbon monoxide. A professional HVAC company will clean the internal parts, check your ductwork, and test for carbon monoxide.

Install Carbon Monoxide Detectors

Carbon monoxide is odorless and colorless, so you may have no idea it’s accumulating until it’s too late – unless you have a detector. Be sure to place one in the basement near the furnace and consider placing one on every floor above.

If you’re concerned about the safety of your furnace or potentially unsafe carbon monoxide levels in your home, you can always call your gas company or an HVAC company. Gas companies also frequently post FAQs and furnace safety tips on their website which can be a valuable resource.

Bottom Line

If the carbon monoxide alarm in your house goes off, get yourself and your family to safety as quickly as possible. In homes without an alarm, check your carbon monoxide levels regularly and learn the early signs of carbon monoxide poisoning so you can take swift action if it becomes necessary.

By monitoring carbon monoxide levels in your home and taking the steps recommended above to prevent accumulation, you can keep yourself and your family safe.