In most states, it is illegal to not have a working carbon monoxide detector in a home that contains a fuel-burning appliance or an attached garage. Roughly 27 states plus the District of Columbia enforce the rule by statute, and about a dozen more reach the same result by adopting the International Residential Code, which has required CO alarms in new homes since 2009. A few states still have no statewide mandate, but cities and counties in those states usually impose their own. Whether you’re the owner, the landlord, or the tenant, the consequences for ignoring the rule run from a citation to serious civil liability if someone is poisoned.
When the Law Actually Applies to Your Home
The legal obligation almost always depends on what is inside or attached to the home. A gas furnace, water heater, gas stove, oil boiler, or wood-burning fireplace will trigger the requirement. So will an attached garage, because car exhaust can seep into the living space. Federal regulations for manufactured housing use the same two triggers: the home must have CO alarms if it contains a fuel-burning appliance or was designed with an attached garage.1eCFR. 24 CFR 3280.211 – Carbon Monoxide Alarm Requirements
All-electric homes without an attached garage are generally exempt from state mandates. That exemption is a legal matter, not a safety one. Carbon monoxide can still enter from outside sources or from a portable generator run during an outage, and generators account for over half of the estimated 204 non-fire CO fatalities in 2021.2U.S. Consumer Product Safety Commission. Non-Fire Carbon Monoxide Deaths Associated with the Use of Consumer Products – 2021 Annual Estimates A battery alarm is cheap insurance if you ever plan to run one.
The timing of when a law applies also varies. Some states cover all existing homes. Others only reach new construction or major renovations. Several states only trigger the requirement at the point of sale.
Where the Alarm Has to Go
Owning an alarm is not the same as complying. Putting it in the wrong location can count as non-compliance by itself. The model fire code adopted in most states requires a CO alarm:
- Outside every sleeping area, within 15 feet of bedroom doors
- On every occupiable level, including basements, with one device allowed to cover multiple requirements on the same floor
- Inside any bedroom that contains a fuel-burning appliance
A single alarm in a hallway can cover several bedrooms, but each story needs its own.3International Code Council. IFC 915.7 Carbon Monoxide Detection and Alarms Systems New construction generally requires hardwired alarms with battery backup, connected to the permanent electrical supply without a disconnect switch.4International Code Council. 2024 International Building Code – 907.6.2 Power Supply Battery-only units are usually acceptable in existing homes. Any CO alarm you install should be listed under UL 2034, the safety standard confirming the device will respond to dangerous concentrations within required time frames.
If You Own and Live in the Home
If you own and occupy your home, the entire obligation falls on you. Buying the alarm and mounting it in the right spot is the easy part. Where owners get caught out is maintenance.
Test the alarm monthly using the test button. Replace batteries the moment the low-battery signal chirps, because that chirp means the unit cannot protect you during a power outage. And replace the detector itself before it expires. Most CO alarms have a lifespan of five to ten years, and the manufacture or expiration date is printed on the back. An expired detector is legally and functionally the same as having no detector at all, because the sensor degrades until it stops responding to carbon monoxide.
If You Rent, or Rent Your Property Out
In rental housing, the obligation splits between two parties who sometimes blame each other after something goes wrong.
The landlord carries the up-front duty. Before a tenant moves in, working alarms must be installed in every required location. Handing a tenant a detector in its packaging does not count. The landlord has to install it.
Once the tenant takes possession, routine upkeep (testing the unit and swapping batteries) shifts to the tenant in most jurisdictions. The tenant also has a corresponding duty to report problems promptly. If the alarm breaks, goes missing, or malfunctions, the tenant should notify the landlord in writing. That notice triggers the landlord’s duty to repair or replace it.
Because a non-functional CO detector is a life-safety issue, most jurisdictions treat a broken alarm as an emergency repair. The landlord typically has 24 to 48 hours to respond after receiving notice, not the longer timelines that apply to a dripping faucet or a sticking door. A landlord who ignores that notice accumulates legal risk with every passing day.
What Happens If You Don’t Comply
The most common enforcement is a citation from a local fire marshal or building inspector, usually with a fine. First offenses tend to run a few hundred dollars. Repeated violations, or failure to correct after notice, can push penalties into the low thousands. A handful of states classify ongoing non-compliance as a misdemeanor, which puts a criminal record on the table in addition to the money.
Fines are not the real risk. The real risk is what happens if someone gets poisoned.
In most states, violating a safety statute creates “negligence per se.” The injured person does not have to prove the owner was careless in some general sense. The statutory violation is the proof. The case moves straight to damages: medical bills, lost income, pain and suffering, and in fatal cases, wrongful death claims by surviving family. Carbon monoxide damages tend to be severe even when the exposure is not fatal, since survivors can suffer lasting neurological injury, and 86 percent of fatal CO incidents happen in home settings.2U.S. Consumer Product Safety Commission. Non-Fire Carbon Monoxide Deaths Associated with the Use of Consumer Products – 2021 Annual Estimates A single incident can produce six- or seven-figure liability.
Landlords face one more trap. Standard commercial general liability policies often contain a “pollution exclusion” written broadly enough to include carbon monoxide. Federal courts have held that CO leaking from a faulty heater into an apartment falls within that exclusion, letting the insurer deny coverage entirely and leaving the landlord personally responsible for the judgment. Any landlord who assumes insurance will absorb a CO incident should read the pollution exclusion in their policy and consider supplemental coverage.
Selling a Home Without One
Some states make CO detector compliance a point-of-sale requirement. In those states the seller must have working alarms installed before closing, regardless of any earlier exemption, as long as the home has a fuel-burning appliance or attached garage.
Even in states without that mandate, a home inspector will flag the absence of alarms, and buyers routinely request installation as a condition of purchase. Installing a $30 detector before listing is cheaper than renegotiating the sale price over an inspection finding that reads as deferred maintenance.