California Carbon Monoxide Detector Rules and Landlord Duties

California’s Carbon Monoxide Poisoning Prevention Act sets the core California carbon monoxide detector requirements: if your home has a fossil-fuel-burning appliance, a fireplace, or an attached garage, you must have working, State Fire Marshal-approved CO detectors installed outside each sleeping area and on every occupiable level. The rule covers single-family houses, apartments, condominiums, and hotel rooms. Because carbon monoxide is colorless and odorless, an alarm is the only reliable way to know the gas is present before symptoms set in.

Which Homes Are Covered

You need detectors if your dwelling contains any one of the following:

A fossil-fuel-burning appliance such as a gas furnace, water heater, stove, or oven that burns natural gas, propane, or fuel oil.
A fireplace, whether wood-burning or gas.
An attached garage, because vehicle exhaust can migrate into the living space.

An all-electric home with a detached garage falls outside the requirement.¹²³

Where the Detectors Must Go

Placement rules are built around catching the gas before it reaches people who are asleep. At a minimum:

Outside each sleeping area, in the hallway or space immediately adjacent to bedrooms.
On every occupiable level of the home, including basements, whether or not anyone sleeps there.

If a bedroom itself contains a fuel-burning appliance, or opens to a bathroom that does, a detector is also required inside that bedroom.⁴ Manufacturers typically recommend keeping additional alarms 5 to 20 feet away from furnaces and water heaters. Follow the instructions that came with your device, since mounting height and distance from corners can affect accuracy.

What Counts as an Approved Detector

Every CO alarm sold in California must be approved and listed by the State Fire Marshal, which requires testing at accredited laboratories before it reaches store shelves.⁵ Beyond the listing, the technical rules turn on whether the building is new or existing.

New Construction

Newly built homes must have hardwired CO alarms powered by the building’s electrical system with battery backup. All alarms in the home must be interconnected so that when one senses carbon monoxide, every alarm in the house sounds at the same time.⁶ That matters in larger homes where an alarm on another floor might otherwise go unheard.

Existing Homes

In existing homes, battery-operated detectors are acceptable as long as any remodeling work does not remove interior wall or ceiling finishes and expose the framing. Once walls or ceilings are opened, hardwired interconnected alarms become required in those areas, because the wiring can be run while the structure is accessible.⁶ For a home not undergoing permitted work, a plug-in or battery unit from any hardware store satisfies the law as long as it carries the State Fire Marshal listing.

Combination Smoke and CO Alarms

A combination smoke and CO alarm that runs on battery power alone must have a sealed, non-replaceable battery designed to last the life of the unit and an end-of-life signal that tells you when to replace the whole alarm. This has applied to combination devices since January 1, 2014.⁷ Standalone CO-only alarms do not currently carry the same sealed-battery rule.

Landlord and Tenant Duties

California splits the responsibility cleanly, and the financial stakes are real on both sides.

Landlord Obligations

Landlords must install working carbon monoxide detectors in every rental unit that has a fuel-burning appliance, fireplace, or attached garage, and must keep them maintained. This obligation is part of the implied warranty of habitability, so a rental without required CO alarms is legally substandard.⁸ When a detector reaches the end of its lifespan, the landlord replaces it.

Tenant Obligations

Tenants must notify the landlord if a detector stops working, starts chirping, or has gone missing.⁹ Don’t just pop the batteries out and forget about it. Written notice creates a paper trail that protects you later.

Tenant Remedies When a Landlord Won’t Act

If you have notified your landlord and nothing has happened in a reasonable time, California offers two main options. You can use repair-and-deduct: buy and install the detector yourself, then subtract the cost from your next rent payment, as long as the cost stays within one month’s rent. This remedy is available up to twice in any 12-month period. You can also withhold rent for a serious habitability violation, though this is a more aggressive step that carries risk if a court later decides the violation was not serious enough. Written documentation of your complaints is essential either way.⁹

Selling or Renovating a Home

When you sell a residential property in California, the home must have functioning CO detectors that comply with current law. Building inspectors verify smoke and CO alarm installation whenever a building permit is issued for any alteration to a residential property, so inspections often happen during pre-sale renovations.¹⁰ Adding a fuel-burning appliance or fireplace to a home that did not previously need CO detectors triggers the installation requirement for the whole dwelling.¹¹

Penalties and Civil Exposure

Enforcement is graduated. A first violation the enforcing agency considers minor typically brings a notice of noncompliance rather than an immediate fine, giving you time to install or fix the detector before penalties apply. Ignore the notice and civil penalties follow. A $200-per-violation figure appears in several local enforcement guidelines, though the amount an agency actually assesses can turn on the severity and duration of the violation.¹²

The fines are the smaller worry. When a tenant or occupant is poisoned in a unit that lacked a required detector, the property owner is an easy target for a negligence lawsuit. The injured person needs to show the owner had a duty to provide detectors, failed to do so, and that the failure caused the poisoning and resulting harm. In a state where CO detectors have been required since 2011, claiming ignorance of the law is not a viable defense. Medical bills, lost wages, and pain-and-suffering damages in CO poisoning cases can easily outrun any regulatory fine.

Keeping Detectors Working

Installing an alarm and forgetting about it is the most common mistake. Sensors degrade over time even when batteries are fine, so the test button can chirp on cue while the sensor itself no longer detects dangerous concentrations reliably.

Test monthly by pressing and holding the test button. A working alarm sounds four beeps, pauses, then four beeps again. If it doesn’t respond, replace the batteries; if it still fails, replace the whole unit.
Replace standalone CO alarms every 7 to 10 years. Check the manufacture date printed on the back. No date and no memory of when you bought it means replace it now.
Listen for the end-of-life chirp. Most modern detectors emit a distinct pattern, often one chirp every 30 seconds, when the sensor is done. This is different from the low-battery chirp and means the whole unit needs to go.

Dust and cooking grease can also interfere with sensors. Vacuuming the vents gently every few months helps prevent false alarms and keeps the sensor responsive.

When the Alarm Actually Sounds

A sounding CO alarm is not a cue to open windows and investigate. Consumer Product Safety Commission guidance is direct: get everyone outside or to a neighbor’s home immediately. Do not stop to ventilate the house unless someone is unconscious and cannot be moved. Once outside, call 911 and do not re-enter until responders confirm the home is safe.¹³

Symptoms start mild and escalate quickly. Early signs look like the flu: headache, dizziness, nausea. Higher or longer exposure brings confusion, disorientation, and memory loss. Severe cases lead to heart rhythm problems, cardiovascular collapse, and death.¹⁴ If anyone in the household has these symptoms when the alarm sounds, tell the 911 dispatcher so paramedics arrive with the fire department.

If evacuation is genuinely impossible due to extreme weather or mobility issues, move to one room with a door or window open to the outside, close all interior doors to the rest of the house, and shut off every fuel-burning appliance you can reach. An exhaust fan in that room helps bring in fresh air faster.¹³

If You Live in Subsidized Housing

Public housing and units receiving federal housing assistance carry an added layer of rules under HUD’s National Standards for the Physical Inspection of Real Estate. Under those standards, a missing or improperly located CO alarm is classified as a life-threatening deficiency that must be corrected within 24 hours. The same 24-hour clock applies when an installed alarm fails to produce an audible or visual signal during testing.¹⁵

HUD’s placement rules closely mirror California’s: near each bedroom, on every floor, and in any area served by a forced-air furnace or adjacent to an attached garage without adequate ventilation. If your property manager hasn’t installed the alarms, the violation is both a state law issue and a federal inspection failure, which gives you extra leverage to force a fix.¹⁵

1
City of San Diego. Carbon Monoxide Alarms
2
City of Dixon, CA. Carbon Monoxide Alarm Information
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California Legislative Information. SB-1394 Dwelling Safety: Carbon Monoxide and Smoke
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Contra Costa County. Residential Smoke and Carbon Monoxide Alarms
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Office of the State Fire Marshal. Building Materials Listing
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City of Covina. Smoke Alarms and Carbon Monoxide
7
San Bernardino County Fire. Frequently Asked Questions on Carbon Monoxide Devices
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California Legislative Information. California Code CIV 1941.7
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California Department of Real Estate. Tenant’s Responsibility for Repairs
10
City of San José. Preparing for Inspection
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Santa Cruz County. Smoke and Carbon Monoxide Alarms Requirements
12
Cornell Law School. California Code of Regulations Title 17 Section 22250 – Penalties
13
U.S. Consumer Product Safety Commission. Responding to Residential Carbon Monoxide Incidents
14
NCBI Bookshelf. Carbon Monoxide Toxicity
15
U.S. Department of Housing and Urban Development. NSPIRE Standard – Carbon Monoxide Alarm