Carbon Monoxide Leak in an Apartment: What to Do

You are settling in for the evening when your CO alarm starts blaring, loud, repeating beeps, not the quiet chirp you are used to. You live on the third floor and you do not even have a gas stove. In a multifamily building that proves nothing: carbon monoxide reaches a unit from a shared boiler room, an attached parking garage or a neighbor's failing appliance, travelling through wall cavities, utility chases and ventilation pathways. The source does not have to be in your apartment for the danger to be real. Two things decide what happens next, and they are the first sixty seconds, and whether your state puts the alarm duty on the landlord or on you.

Quick Safety Summary

• If a CO alarm activates in your apartment, treat it as real, leave immediately with everyone (including pets).
• CO is odorless, "I don't smell gas" does not mean it is safe.
• Notify building management and neighbors, CO can affect multiple units.
• Do not re-enter until authorities or a qualified technician confirm the building is safe.
• Document everything: date, time, alarm model, symptoms, and official readings for follow-up.

Step-by-Step: What to Do Right Now

For the expanded emergency checklist: what to do if a CO alarm goes off.

What Not to Do

• Don't ignore it because you "don't smell gas." CO has no smell. The odorant you associate with gas leaks (rotten eggs) is added to natural gas, it is a different hazard.
• Don't stay inside to "air it out" if anyone has symptoms.
• Don't assume it is a false alarm until it is verified by someone with a calibrated meter.
• Don't silence the alarm and go back to sleep. If the alarm fully activated (rather than a brief maintenance chirp), it detected something. For chirp vs alarm patterns, see CO detector beeping.

Where Apartment CO Can Come From

In a single-family home, the CO source is almost always inside your own building. In apartments, the possibilities are wider:

• Shared boiler or furnace room, combustion gases can enter units through vents and utility chases.
• Attached or underground parking garage, vehicle exhaust can infiltrate upper floors through stairwells, elevator shafts, and gaps in the structure.
• A neighbor's appliance, a malfunctioning gas stove, water heater, or unvented space heater in an adjacent unit.
• Backdrafting from shared venting, when exhaust that should go up the flue is pulled back into the building by wind or pressure imbalances.
• Construction or renovation nearby, fuel-burning equipment used during work on the building or adjacent properties.

Because the source may be outside your control, building-level investigation is essential. A CO alarm in your unit does not necessarily mean your appliances are the problem, but it does mean something in the building is producing or channeling CO into your living space.

Who to Call: Practical Contact Order

1. Emergency services (fire department), if anyone has symptoms, if the alarm is sounding, or if you cannot quickly identify a safe cause.
2. Building management or security, to check shared boilers, garages, vents, and other common sources. They may need to evacuate other units.
3. Licensed HVAC technician, to inspect your furnace, water heater, stove, and venting after the immediate emergency is resolved.
4. Your utility company, if a gas leak is also suspected (rotten egg smell in addition to the CO alarm).

After the Emergency: Inspection, Documentation, and Prevention

Once the immediate danger is addressed, focus on preventing repeat events. In multifamily buildings, root causes may involve shared venting, backdrafting, mechanical room issues, or garage exhaust infiltration.

Document everything

• Date and time of the alarm activation.
• Which alarms activated and in which rooms.
• Symptoms experienced by anyone in the unit.
• Any official CO readings provided by responders.
• Photos of the alarm model, display messages, or error codes.

Request written follow-up

Ask building management for written confirmation of inspections and repairs. This is important for your records and may be relevant if the issue recurs or if you need to involve local housing authorities.

Review your CO alarm setup

Replace any alarm that is past its end-of-life date. Verify placement near sleeping areas and on every occupied level of your unit. For planning, see how many CO detectors do I need and where to place a CO detector.

Renter Rights and Landlord Responsibilities

Almost every US state recognizes an implied warranty of habitability that obligates landlords to maintain rental units fit for human occupancy. The duty generally covers heating, ventilation, working fuel-burning appliances, and the alarms that protect occupants from the byproducts. Most state CO statutes layer on top of that warranty with specific alarm-installation requirements before occupancy and ongoing maintenance to a defined standard. Tenants are typically expected to test alarms and report issues; replacement responsibility varies by local law and lease terms.

Alabama is the state usually named as the exception, and every legal summary in this corner of the internet repeats it, including the one this page cites below. The shorthand stops one step too early to be useful to somebody renting there. What Alabama never adopted is the judge-made warranty. It did adopt the Uniform Residential Landlord and Tenant Act, and Code of Alabama section 35-9A-204 puts a statutory duty on the landlord to maintain fit premises, with tenant remedies at section 35-9A-401 that run to damages, rent reduction and lease termination once fourteen days of written notice have passed. The route is a statute rather than a common-law warranty, which is a different road to a similar place and not the dead end the shorthand suggests.

A practical approach that reduces risk regardless of who is technically responsible: test your alarms monthly, report chirps and faults to management in writing (email creates a paper trail), and keep at least one battery-powered CO alarm in your unit even if the building provides hardwired units. During a power outage, when heating risks rise, hardwired alarms without battery backup go silent exactly when you need them most.

Why Apartments Are Different: Allen Benedict Court, January 17, 2019

The strongest single argument for apartment-specific CO awareness comes from the Allen Benedict Court Apartments in Columbia, South Carolina. On January 17, 2019, residents Calvin Witherspoon Jr. (62) and Derrick Caldwell Roper (31) were found dead in their units. The Columbia coroner attributed both deaths to carbon monoxide poisoning. Columbia Fire Department Chief Aubrey Jenkins wrote to the housing authority the next day, 18 January, and the inspection behind that letter counted, in his own figures, "63 apartments with carbon monoxide or natural gas detected, 411 individuals evacuated, and 17 pets evacuated". The follow-up inspection documented what the city called an unprecedented 869 code violations across the property: missing or non-functioning smoke detectors, no carbon monoxide detectors in any unit despite city and state fire-code requirements, exposed wiring, stoves leaking natural gas, expired fire extinguishers, and unmaintained furnaces. More than 50 former residents later sued the Columbia Housing Authority; a $2 million settlement on behalf of the Witherspoon family was approved in federal court in October 2023.

Two operational lessons sit inside that case. First, the failure was building-wide: the same vent failures, missing alarms, and deferred maintenance affected every unit, not only the two where deaths occurred. Tenants in single-family homes can sometimes inspect their own appliances; apartment tenants almost never can, which is why landlord duties and city inspection regimes are the real protection layer. Second, the alarm rule existed before the deaths. South Carolina fire code required CO detectors; the housing authority had not installed them. Statutes on paper do not protect people if no one enforces them. Apartment dwellers can supplement with a battery-powered portable CO alarm at their bedside while the building-level fix works through legal and political channels.

Three Tiers of Landlord Liability

Civil liability for CO incidents in rentals generally tracks one of three categories, distilled from publicly available legal analyses by AllLaw, Nolo, and personal-injury firms working CO cases. None of this is legal advice; it is a framework for understanding what cases have looked like.

The pattern across recent recoveries (Allen Benedict $2M, Mexico City Airbnb wrongful-death claims, Best Western Boone civil settlements) is that the operator's inspection records are the most consequential exhibit. Detailed logs of monthly alarm tests, dated technician inspections, and prompt response to complaints move a case from tier 1 toward tier 3.

State Tenant-Rights Cross-Reference

Landlord duties and tenant remedies sit in habitability statutes and CO detector laws that vary by state, and the split between the two sides varies with them. The full per-state breakdown lives in our CO detector laws hub and the rental CO detector requirements overview.

The split decides what your own next move costs you. Where the tenant carries battery maintenance, pulling a battery to stop a chirp you have not identified can move responsibility for whatever follows onto you. Where the owner carries replacement after notice, a dated written report starts a clock somebody else has to answer. Those are different actions, and which one applies is a question about your jurisdiction rather than about your building.

Sources & References

• CPSC: Carbon Monoxide Information Center
• CDC: Carbon Monoxide Poisoning Prevention
• NFPA: Carbon Monoxide Safety
• WIS-TV, Coroner: Allen Benedict Court deaths ruled CO poisoning (January 28, 2019)
• WIS, Conditions at Allen Benedict Court made a clear and imminent threat, fire chief letter (24 January 2019), for the evacuation figures quoted above
• WIS-TV, $2 million settlement reached in Allen Benedict Court death lawsuit (October 2023)
• AllLaw / Nolo, Carbon Monoxide Exposure and Landlord Liability (three-tier framework reference)
• Code of Alabama section 35-9A-204, landlord to maintain fit premises, and section 35-9A-401, tenant remedies for noncompliance, both in the Alabama Uniform Residential Landlord and Tenant Act. Given as plain text rather than as a link: the canonical copy our records use is on a host that blocks automated checking and opts out of archiving, so a link here could not be verified by the same sweep that checks the rest of this list.

Last updated: August 12, 2026