Carbon Monoxide Detector Requirements In Colorado (CO Detector)

Date Published: September 3, 2019

When buying or building a home, carbon monoxide detector requirements can get a little tricky. Each state has a slightly different code requirement, older houses and newer houses can have different needs, and there are rules on placement too!

But following these rules is very important because a CO detector can save your life. Roughly 400-500 people die every year from carbon monoxide poisoning, and over 50,000 people are sent to the hospital over it according to the CDC.

To prevent this issue, carbon monoxide detector requirements were created, and we are going to break them down below.

Graphic about co related deaths in the US. Carbon monoxide detector requirements can prevent this.

Image from

What Are The Carbon Monoxide (CO) Detector Requirements In Colorado?

Short answer: You need them. 

Every house built in Colorado is required to have a CO detector.

As of July 1, 2009, Governor Bill Ritter signed into law Colorado House Bill 1091 which states that all dwellings that are built, rented, remodeled or sold must have a carbon monoxide detector installed.

This is required on all homes that have a fossil fuel burning device for heat, a fireplace of any kind, or an attached garage.

All of these configurations can generate carbon monoxide which can escape into the home if not properly mitigated. So it is very important to keep your CO detectors in place and in working condition.

The only exception to this rule is in multi-family properties where there may be a global fire alarm and CO detection system in place. If this is the case, your HOA/property management company will need to follow their own guidelines.

If you are buying a home and have a home inspection performed through Scott Home Inspection, we call out missing detectors and state that they are required to be installed. By Colorado law, the seller must install the units before the sale is completed.

If you are moving into a brand new home, the builder will be required to install CO detectors, and they will be checked for during their “certificate of occupancy” inspection.

Where Do I Place the Detectors?

Colorado Law states that the detectors need to be placed within 15 feet of all sleeping rooms.

If all the bedrooms in a home are located in the same hallway, only one detector is needed in the hallway. This can be a stand-alone unit or a combination with the smoke alarm.

Carbon monoxide detector requirements state that this is the only location necessary. However, this applies to all sleeping areas. So if you have bedrooms on every floor of your home, you will need a detector outside of each one.

Smoke and CO Detector Placement Floor Plan as state in the Boulder Rental License Requirements Carbon Monoxide detector requirements in colorado

One common misconception is that you need a detector on every floor. This is not the case unless there is a bedroom on each floor as well.

Another common place we see additional CO detectors is in a home’s utility room.

This is a best practice that we also recommend that people do. It is a good idea to place a detector close to the most common source.

However, this location is not required in Colorado law and you cannot force a seller to install a unit here.

What is Carbon Monoxide and How Does It Get Into Your Home?

Carbon monoxide is a gas formed from the exhaust of burning combustible objects. This includes natural gas, gasoline, and wood among other items.

When the combustible materials are not fully burned, the excess result is carbon monoxide.

Typically, this exhaust is well mitigated through flue pipes and airways but occasionally these pathways are obstructed or compromised and carbon monoxide can flow back into a home.

One simple example of this is when a car is running in a garage, but the door leading into the home is open. The exhaust from the car can move into the home and can be inhaled by the occupant.

A more complicated and unfortunately more common example would be a furnace exhaust issue.

A furnace needs oxygen to burn gas within the unit to produce the flame. Older furnaces pull this oxygen from the air within the room they are installed in.

If the room does not have a proper air supply, (i.e. it is placed within a closet with no makeup air return vent) then the furnace will begin to use up all the oxygen within the space.

Diagram of a furnace backdrafting. One case of carbon monoxide detector requirements.

Once the oxygen is depleted, the burning flame will create a negative pressure within the room which will draw air from any possible location.

In the case of the sealed closet, the only place air can come from is from the exhaust line. This is called a backdraft.

Because air is pulled down the exhaust line, the carbon monoxide and other exhaust fumes have nowhere to go but into the home.

When we inspect homes, this is a common issue that we are on the lookout for. All small utility closets and rooms should have a combustion air supply pipe that will provide your fuel-burning devices with makeup air.

Older Furnaces and Carbon Monoxide Detectors

Older furnaces are a trigger for us to pay extra special attention to carbon monoxide levels.

Although carbon monoxide detector requirements are the same regardless, it is even more important to have one in place when your furnace is aging.

As a furnace gets older, rust can build up on the heat exchanger which can eventually lead to cracking. Cracks in a heat exchanger can mix exhaust and carbon monoxide with the regular airflow of a furnace.

This means the blower of your furnace can be pushing dangerous levels of CO through your ducts! But not to worry. This is somewhat rare and a CO detector would catch harmful levels long before they could harm you.

However, if your furnace is older we recommend you get it serviced and evaluated regularly to ensure this issue is not occurring.

In our inspector’s tool bag, we have a very sensitive, handheld carbon monoxide detector with a level display that will tell us if there is any CO coming through your duct system.

Carbon Monoxide Maintenance

Not only should detectors be installed in the correct places when buying, selling, or renting a home, but they should also be maintained over time.

It doesn’t do anyone any good to have a unit run out of batteries or worse, be taken down to get rid of the “chirp.”

Batteries should be changed regularly, and the units should be tested at least quarterly.

Also, most detectors have a 10 year expiration date. Newer models will begin to beep constantly even with fresh batteries installed if they do expire.

Older units may not have this feature, so be sure to check the back of the unit for the manufacture date, and replace as needed.

Finally, we hope that your carbon monoxide detectors never have a reason to sound their alarms, but if they do, exit the house immediately and call a professional.

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About the Author: Chris Scott

Chris Scott is an ASHI certified home inspector with multiple years of experience in home inspections, blower door testing, duct leakage testing, and Boulder Rental License Inspections. Chris is also the Website Coordinator for Scott Home Inspection.

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