Colorado’s carbon monoxide detector law requires an operational CO alarm within 15 feet of every room used for sleeping in any home that has a fuel-burning appliance, a fireplace, or an attached garage. The rules sit in Title 38, Article 45 of the Colorado Revised Statutes and apply to single-family homes being sold, rental units at a change of tenancy, and any residence undergoing permitted interior work after July 1, 2009. There are no state criminal penalties for ignoring the law, but noncompliance strips away a statutory liability shield and leaves owners exposed to civil claims if someone is harmed.1CRS 38-45-101 through 38-45-106
Which Homes the Law Covers
Two physical features put a home under the statute: a fuel-burning heater, appliance, or fireplace, or an attached garage. “Fuel” is defined broadly and includes coal, kerosene, oil, gas, wood, and other hydrocarbons that produce carbon monoxide when burned. A home that is entirely electric and has no attached garage is not covered. If an all-electric home later adds a gas furnace, wood-burning fireplace, or other fuel-burning appliance, the requirement kicks in at that point.
The law applies only once a triggering event occurs on or after July 1, 2009. For single-family homes, that trigger is a sale or the issuance of a building permit for interior work, appliance replacement, or the addition of a sleeping room. For rentals, it’s a building permit for interior work or any change in tenant occupancy. Multi-family buildings — condominiums, cooperatives, and apartment buildings with more than one dwelling unit — follow the same placement rules.
An owner-occupied home that has not been sold, rented, or renovated since before July 1, 2009 is technically outside the statute. The carbon monoxide risk is the same, so installing alarms is still advisable, but the legal obligation hasn’t attached.
Where Alarms Must Be Installed
The core rule is in CRS 38-45-102: a carbon monoxide alarm must be installed within 15 feet of the entrance to each room used for sleeping. If bedrooms are on different levels, each level needs at least one alarm covering those sleeping areas.
The statute also allows alarms to be placed “in a location as specified in any building code adopted by the state or any local government entity.” Your city or county may require more than the state baseline — alarms on every habitable level, for example, or alarms near specific fuel-burning appliances regardless of bedroom proximity. Homes with fuel-burning appliances in isolated spaces like basements may need extra alarms, particularly where a local code adopts National Fire Protection Association standards. NFPA guidelines recommend an alarm on every level and near potential CO sources.
What Counts as an Approved Alarm
A compliant device must produce a distinct audible alarm and be listed by a nationally recognized independent testing laboratory such as UL. Combination smoke-and-CO alarms are allowed, but the unit has to clearly distinguish the two hazards through different alarm sounds or voice signals.
Four installation methods qualify: hardwired into the home’s electrical system, plugged into an outlet with battery backup, wired with battery backup, or connected to an electrical panel. Battery-powered alarms are also permitted when mounted on the wall or ceiling in accordance with NFPA Standard 720.
Carbon monoxide sensors degrade. Most manufacturers rate their alarms for about seven years, after which the sensor becomes unreliable. Alarms produced after August 2009 include an end-of-life chirp when the unit needs replacement. Check the manufacture date and replace the alarm when the recommended lifespan expires, even if it still appears to work.
If You’re Selling a Home
The seller of any single-family home offered for sale on or after July 1, 2009 must install an operational CO alarm before closing if the home has a fuel-burning appliance, fireplace, or attached garage. Placement follows the 15-foot rule unless a local code specifies otherwise.
Home inspectors routinely flag missing or expired alarms, and buyers typically require installation as a condition of closing. If a sale proceeds without compliant alarms and someone is later harmed, the seller can face civil liability. CRS 38-45-106 preserves a purchaser’s remedies against a non-compliant seller even when a real estate licensee has otherwise followed the rules.
If You’re a Landlord
Before a new tenant takes possession, the landlord must replace any carbon monoxide alarm that was stolen, removed, missing, or not working after the previous tenancy, and must provide the batteries needed to make the alarm operational. That obligation hits at every change in occupancy.
Once a tenant is in place, the landlord’s ongoing duty is triggered by written notice. If the tenant notifies the landlord in writing that an alarm is missing, stolen, or not working, the landlord must replace it. If the tenant reports a deficiency the tenant cannot fix, the landlord must correct it. Outside those specific situations, the statute says the landlord is not responsible for routine maintenance, repair, or battery replacement.2CRS 38-45-104
A verbal complaint does not trigger the statutory duty. Landlords who want a clear record — and tenants who want legal protection — should insist that CO alarm issues come in writing.
If You’re a Tenant
Tenants carry the day-to-day maintenance burden. You must keep, test, and maintain the alarms in your unit. When batteries need replacement, notify the landlord in writing. If an alarm goes missing, stops working, or has a deficiency you cannot correct, written notice to the landlord is required.
The law prohibits anyone from removing batteries or disabling a carbon monoxide alarm except during inspection, maintenance, or repair. A tenant who disables an alarm takes on responsibility for any resulting harm and may be liable for replacement costs. Test your alarms monthly with the test button. It takes a few seconds.
Penalties and Liability for Noncompliance
Article 45 does not create criminal penalties. What it creates, in CRS 38-45-106, is a liability shield: no one can bring a claim against a property owner, their agent, or an installer for damages resulting from the operation, maintenance, or effectiveness of a CO alarm if that person installed the alarm according to the manufacturer’s instructions and the law’s requirements.
If you fail to install alarms as required and someone is harmed by carbon monoxide exposure, you lose that protection. Ordinary negligence claims become available, which can reach medical expenses, lost wages, pain and suffering, and wrongful death damages. Courts don’t need a specific penalty statute to hold a landlord or seller accountable when a safety requirement exists and was ignored.
Noncompliance can also trigger local enforcement. CRS 38-45-105 explicitly allows municipalities and counties to adopt their own carbon monoxide alarm ordinances, and many Colorado cities have done so. Denver passed its own ordinance in 2009 alongside the state law. Violations under local codes can bring citations, fines, or correction orders, and some cities escalate fines for repeat violations. Local code enforcement officers — not a state agency — typically investigate complaints.
How to Report a Violation
If you’re a tenant with a missing or broken alarm, start with written notice to the landlord. That step is what triggers the landlord’s statutory duty to act. Keep a dated copy of every notice you send.
If the landlord does not respond, report the issue to your local building code enforcement office or housing authority. Local agencies can investigate and order the landlord to correct deficiencies, and in cities with their own CO ordinances, local enforcement may carry additional penalties beyond what state law provides.
Homebuyers who discover missing alarms during inspection can require installation as a condition of closing. If a sale closes without compliant alarms and the buyer later suffers CO exposure, the buyer may have a civil claim against the seller. In severe cases, where a landlord has repeatedly ignored reports and someone is injured or killed, local prosecutors can pursue action based on general negligence principles even though Article 45 itself does not impose criminal penalties.
A Note on Federally Assisted Rentals
Rental units receiving Section 8 Housing Choice Voucher or Project-Based Voucher assistance are also subject to HUD’s NSPIRE inspection standards, which are stricter than Colorado’s state law. CO alarms must be installed in the immediate vicinity of each bedroom, or inside each bedroom, when the unit contains a fuel-burning appliance or fireplace. A missing, improperly placed, or nonfunctional alarm is a life-threatening deficiency: the unit fails inspection and the landlord has 24 hours to correct it.
NSPIRE goes further in two situations state law does not specifically address. If the unit is served by a forced-air furnace located elsewhere in the building, an alarm is required near each bedroom, inside each bedroom, or in the room with the first duct register. If the unit sits one story or less above or below an attached private garage that lacks proper ventilation, an alarm is required near or inside each bedroom regardless of whether the unit itself contains fuel-burning appliances.