Carbon monoxide detectors are required by law in most U.S. homes, though the exact rule depends on where you live and what’s inside the house. Nearly every state has a CO detector statute, and the requirement almost always kicks in when a home contains a fuel-burning appliance, a fireplace, or an attached garage. There is no single federal law covering all properties, but federal housing programs, state statutes, and local ordinances together reach the vast majority of occupied dwellings.
Which Homes Fall Under the Requirement
The trigger across jurisdictions is almost always the presence of a carbon monoxide source. That includes a gas furnace, oil-fired boiler, wood-burning fireplace, propane water heater, kerosene space heater, or similar fuel-burning equipment. Homes with an attached garage also qualify in most places, because vehicle exhaust can seep into living spaces even when the garage door is closed.
All-electric homes with no fireplace and no attached garage are generally exempt. Under the framework used by the International Fire Code, CO detection is not required in a dwelling that has no CO source and no connection to a garage. The exemption isn’t universal, though. Some local ordinances require detectors in every residential unit regardless of fuel source, so an all-electric home in one city may still need alarms. Your local fire department or building code office can confirm which rule applies to your address.
State and Local Rules Do Most of the Work
The real regulatory weight sits at the state level. The vast majority of states have enacted CO detector legislation, though the details vary considerably. Some states require detectors only in new construction. Others extend the mandate to all existing homes. A number of states tie the requirement to a specific event: the sale of the property, the start of a new rental agreement, or a building permit for renovation work. The common thread is that the mandate activates when there’s a fuel-burning appliance, a fireplace, or an attached garage.
Local governments often go further than state law. More than two dozen municipalities had their own CO detector ordinances on the books as of the last comprehensive count, and more have adopted them since. A city rule might require detectors in every residential unit regardless of fuel source, even when the state baseline only covers combustion-equipped homes. Because local ordinances can be stricter than state statutes, checking both is the only reliable way to know what applies to your property.
Federally Assisted Housing Has Its Own Rule
There is no federal law requiring CO detectors in all residential or commercial properties. Federal requirements exist only for certain government-assisted housing. The Consolidated Appropriations Act of 2021 amended the rules for HUD programs, including Section 8 and the Housing Opportunities for Persons With AIDS (HOPWA) program, to require carbon monoxide detectors in federally assisted dwelling units. The requirement took effect December 27, 2022.1U.S. Department of Housing and Urban Development. Notice CPD-22-15 – Carbon Monoxide Detection Requirements
Each covered dwelling unit must have CO alarms or detectors that meet or exceed the standards in Chapters 9 and 11 of the 2018 International Fire Code. The rule applies to units receiving rental assistance, units in rehabilitated or newly constructed buildings, and units receiving short-term rent or utility payments through covered programs.1U.S. Department of Housing and Urban Development. Notice CPD-22-15 – Carbon Monoxide Detection Requirements Units that contain no CO source and have no connection to a garage can qualify for an exemption, but the housing provider has to document that it applies.2HUD Exchange. Carbon Monoxide Detection in HOPWA-Assisted Units Webinar Questions and Answers
Landlord and Tenant Responsibilities
In rental properties, the landlord is almost always responsible for installing working CO detectors before a tenant moves in. Many state laws specifically require functioning detectors to be in place at the start of each new tenancy. When a detector fails or reaches end of life, replacement typically falls on the landlord as well.
Tenant obligations are narrower but real. They generally include testing the alarm periodically, replacing batteries when needed, and notifying the landlord promptly if a detector stops working. Tenants are also expected not to tamper with or remove the devices. If a tenant disables a detector and a CO incident follows, the landlord’s liability may shift. Lease agreements should spell out who handles battery replacement, and both sides should keep records of any maintenance or replacement work.
Selling a Home
A growing number of states require working CO detectors as a condition of selling a home. In these jurisdictions, the seller must certify that detectors meeting current standards are installed and functional before closing. Some states apply this to all residential sales. Others limit it to homes with fuel-burning appliances or attached garages. The rule can also reach for-sale-by-owner transactions, not just agent-listed properties.
If you’re buying, your inspector should check for CO detectors as part of a standard inspection. Don’t lean on that alone. Confirm that installed detectors haven’t passed their expiration date and that they’re placed where state law requires. A detector that’s present but expired doesn’t satisfy the law.
Where the Law Says to Put Them
Placement rules are fairly consistent because most jurisdictions build on the same model codes. CO detectors should be installed on every level of the home and outside each sleeping area.3U.S. Consumer Product Safety Commission. CO Alarms The NFPA recommends a central location outside each group of bedrooms, plus one on every occupied floor.4National Fire Protection Association. Carbon Monoxide Safety If you’re only installing one, the EPA advises placing it near the bedrooms and making sure the alarm is loud enough to wake you.5U.S. Environmental Protection Agency. Where Should I Place a Carbon Monoxide Detector
The CPSC recommends against installing detectors in attics or basements unless those spaces include a sleeping area.3U.S. Consumer Product Safety Commission. CO Alarms A detector can be mounted on the ceiling or on a wall within 12 inches of the ceiling. Keep it away from windows, exterior doors, and areas with heavy air movement that could skew the sensor.
What Counts as a Compliant Detector
Any detector you install should be certified to Underwriters Laboratories Standard 2034 (UL 2034) or the International Approval Services 6-96 standard. Those certifications ensure the alarm triggers before CO reaches dangerous levels and that it won’t fire on brief, harmless spikes.6US EPA. What About Carbon Monoxide Detectors UL 2034 covers both fixed and portable CO alarms and sets sensitivity thresholds at specific concentration levels.7UL Standards and Engagement. Carbon Monoxide Protection Look for the certification label on the packaging before you buy.
Power source rules depend on whether the home is new construction or existing. Model building codes generally require new homes to have hardwired CO alarms with battery backup, and most codes also require interconnection so that when one alarm triggers, every CO alarm in the home sounds. Existing homes typically get more flexibility, with battery-operated or plug-in detectors usually permitted if the home predates the local law. Combination smoke and CO alarms are allowed in most places, provided the device meets the certification standards for both functions.
Penalties and Liability for Non-Compliance
Fines for failing to install required CO detectors vary by jurisdiction but generally run from a few hundred dollars to $1,000 or more per violation. Many jurisdictions give property owners a notice period to correct the problem before imposing a fine, so the first consequence is often a warning. Repeat violations or failure to fix after notice usually carry steeper penalties.
The civil exposure is the larger risk, and it falls hardest on landlords. A tenant injured by carbon monoxide in a unit without a required detector has a strong negligence claim, and the absence of a legally mandated safety device makes a defense difficult. At higher concentrations, carbon monoxide causes impaired vision, confusion, and loss of coordination; at very high concentrations, it is fatal.8U.S. Environmental Protection Agency. Carbon Monoxide’s Impact on Indoor Air Quality Against that, the cost of a code-compliant detector is small.