How Far Should a Carbon Monoxide Detector Be from a Furnace?

If carbon monoxide (CO) leaks into the home, it’s crucial that a family be alerted by the use of a CO detector. So, how far should a carbon monoxide detector be from a furnace?

A carbon monoxide detector should be between 5 to 20 feet from a furnace, fireplace, water heater, or any other appliance that emits the deadly CO gas. Every level of the home should be equipped with a carbon monoxide detector, as well as just outside of all sleeping areas.

Furnace Doctor

Each CO detector location should be free of anything that might hinder its access and allow for protection against other unclean environmental influences. Placing a carbon monoxide detector near a door or window is highly discouraged.

Can a Furnace Cause Carbon Monoxide

Furnaces can cause carbon monoxide, becoming what the CDC refers to as the silent killer. As cold winters arrive, furnaces burn gas and oil to keep us warm. When a furnace is working properly, any CO generated is vented to the outside. A CO leak, however, allows poisonous CO gases into the home and puts families at risk.

Should You Put a Carbon Monoxide Detector Near Your Furnace

You should put a carbon monoxide detector near your furnace, ideally between 5 and 20 feet away. CO gas leaks are particularly prevalent at night when furnaces are running continuously to keep our homes warm. The possibility of being exposed to a leak while we sleep is eliminated with a carbon monoxide detector.

Can a Broken Furnace Cause Carbon Monoxide

A broken furnace can cause carbon monoxide to enter indoors where it shouldn’t. A properly functioning furnace is designed to vent the CO outside so it does not enter the home. When a furnace is broken, this can cause the carbon monoxide to mingle with the indoor air supply, leading to CO poisoning.

Can a Furnace Leak Carbon Monoxide When Turned Off

A furnace that is turned off cannot leak carbon monoxide. However, if there is CO being emitted into the air from another location within the home, the CO can go through the furnace, down the air ducts, and seep through any holes in those ducts.

How to Fix a Carbon Monoxide Leak in a Furnace

It’s not uncommon for a furnace to have a carbon monoxide leak in need of repair. Leaks are a result of cracks in the furnace’s heat exchanger or flue supply pipes. If a furnace leaks and isn’t fixed quickly, it could be the difference between a family member living or dying.

Clogged filters that lead to blocked pathways can also cause carbon monoxide leaks. With the buildup of CO, over time it will find its way out and into the air you breathe.

8 Steps to Fix a Carbon Monoxide Leak in a Furnace

Let’s go over the steps needed to address and fix the CO leak in the furnace by following the step-by-step guide below:

Step 1. Open Windows for Good Ventilation

The first thing you should do before anything else is to open doors and windows to ensure proper ventilation while you are working in the area of the furnace leak.

Step 2. Turn Off the Furnace

At your heating control panel, turn the switch to OFF.

Step 3. Install a Cabron Monoxide Detector

If you didn’t already have a CO detector, now’s the time to run to the store and install one. Having a carbon monoxide detector is one of the best ways to protect yourself against CO poisoning.

Step 4. Find the Leak

Inspect the furnace for small openings such as cracks, holes, rusty spots, areas around old, worn-out gaskets, and such.

To confirm a leak, use a penetrating dye and spray it over the areas of concern. The Ozone Hole recommends using a product called Magna flux. This method helps to locate any suspicious leaks.

Step 5. Replace Weak or Compromised Furnace Parts

After locating all areas of concern, start replacing those furnace parts. If there are areas on the furnace that are not currently leaking yet look bad, take the time now to replace them, saving yourself the headache of having to do another repair later.

Step 6. Replace or Wash Dirty Furnace Filter

Whether your carbon monoxide leak was due to your dirty filter or not, now’s a great time to replace or wash your furnace filter. You’ll walk away knowing your efforts were complete and thorough.

Step 7. Restart Your Furnace

Turn your furnace back on and inspect again for any CO leaks.

Step 8. Call a Professional

If you still suspect a carbon monoxide leak, it’s time to turn the furnace back off and call a professional.

Can a Dirty Furnace Filter Cause Carbon Monoxide

A dirty furnace filter can cause carbon monoxide poisoning in a home, yet replacing furnace filters is commonly overlooked by many homeowners. Some homeowners don’t even realize they have a filter that would need to be replaced. As furnace filters clog, toxic CO is created, creeping into homes.

Carbon Monoxide from a Boiler

When there is not enough oxygen for the fuel to burn fully in a boiler, carbon monoxide is created. Boilers use a flue to expel the carbon monoxide they create outside the house. Occasionally, this gas can leak from the boiler system into the house and harm people with carbon monoxide.

Can an HVAC Cause Carbon Monoxide

Although HVAC systems include both heating and cooling, the air conditioning part of your HVAC cannot cause carbon monoxide. Air conditioners do not burn fuel; therefore, they are unable to emit CO gas. The furnace component of your HVAC system, however, can indeed produce carbon monoxide.

Where Is My Furnace

Your furnace is usually located in the center point area of your home, commonly found in garages, attics, basements, crawlspaces, or utility closets. In apartments, your furnace may be hidden in the storage room near your back porch area.

HVAC vs. Furnace

An HVAC system provides heating and cooling, as well as other functions while a furnace provides only one function, heating. The two similarities between the HVAC and a furnace are they both require a sophisticated duct system and are both designed to maintain a comfortable temperature within the home.


Trina Greenfield, Author
SmackDown Media LLC

About the Author:
Trina Greenfield, the owner of SmackDown Media LLC, is passionate about providing information to those interested in the air quality in and around their homes. Trina writes content about things she’s passionate about, such as safe, in-home air, educational platforms for children and adults, as well as all things family-related.