Selling a Colorado home with a fireplace: the CO alarm law and the chimney

Denver Fireplace & Chimney · October 12, 2026

What the law requires

Colorado's carbon monoxide alarm law is C.R.S. 38-45-102. For any existing single-family home offered for sale or transfer on or after July 1, 2009, the seller must make sure an operational carbon monoxide alarm is installed within 15 feet of the entrance to each room lawfully used for sleeping. It applies if the home has a fuel-fired heater or appliance, a fireplace, or an attached garage.

That covers nearly every house in the Denver metro. Census ACS data shows utility gas heats 61 to 77 percent of homes in every city we serve, and a gas furnace or water heater alone triggers the rule. A fireplace of any type, wood or gas, triggers it on its own.

What it does not require

We searched Colorado and Denver law and found nothing that requires a chimney inspection, sweep or certificate to sell a house. Any company telling you a chimney inspection is legally required to close in Colorado is mistaken.

It is still a common request. A buyer's home inspector will usually note an unused or stained fireplace and suggest a specialist look at it, and buyers often ask about a wood stove's age and type. An inspection done before listing lets you fix what's found, or price it in, on your own schedule instead of in the middle of negotiations.

The alarm rule also covers renovations and rentals

The same section applies when interior alterations, repairs, fuel-fired appliance replacements or additions that need a building permit are done on a single-family home. So if you replace a gas fireplace, install an insert or swap a furnace before listing, the carbon monoxide alarms have to be in place as part of that permitted work.

Landlords have a parallel duty under C.R.S. 38-45-104. Rentals need the same alarms when permitted work is done or a new tenant moves in, and the landlord replaces missing or dead alarms before a new tenancy and supplies batteries.

A seller's checklist for the fireplace and chimney

Do these before the listing photos, not after the buyer's inspection report:

• Install or test carbon monoxide alarms within 15 feet of every bedroom door. Write down where they are for your disclosure paperwork.
• Get the chimney and fireplace inspected with photos, so you know what a buyer's inspector will see.
• Fix water first. Stains near the chimney, a cracked crown (typically $600–$2,200 to repair) or failed flashing ($300–$1,800) are what buyers worry about most.
• Replace a missing or damaged cap ($250–$850) or a rusted chase cover ($300–$700). Both show in listing photos and from the street.
• Make sure the gas fireplace lights, the damper opens and closes, and the remote works. A gas fireplace service typically runs $150–$350.
• Know what kind of wood stove you have. CDPHE says a used, uncertified stove can't be sold on its own in the seven-county metro, and buyers may ask whether yours is EPA-certified.

What buyers should look for

If you are buying, the alarm law gives you a quick check: walk the bedrooms and look for carbon monoxide alarms within 15 feet of each door. Then look at the chimney from the street. A brick chimney with broken corners, flaking brick or white staining near the top has been taking on water. A newer home's chase with rust streaks running down the siding has a failing chase cover.

Ask whether the fireplace is wood or gas, and if wood, whether it is an open fireplace or an EPA-certified insert. In Denver and most of the metro, an open fireplace can't be used on Action Days, which can be called from November through March, according to CDPHE. That affects how much you will actually use it.

Our inspection for a sale

Our inspection is free. We go top to bottom, photograph what we find and give a written price for anything that needs work, so a seller can fix it or a buyer can negotiate with real numbers. If a hidden problem is suspected inside the flue, a camera scan is priced at the inspection. We work Sunday to Friday in 3-hour windows, and we call to confirm.