Best Carbon Monoxide Detectors of 2026: Plug-In, 10-Year, Combo and Smart

How we chose carbon monoxide detectors

Every pick had to pass five tests, taken from CPSC and NFPA advice and from the makers' own data sheets and user guides. Every figure on this page comes from those documents or from the UL 2034 standard.

• Listed to UL 2034. CPSC says to install a CO alarm that meets the current UL 2034 standard, and NFPA says to choose one listed by a qualified testing laboratory. Kidde's data sheets list UL 2034 for every Kidde pick (the Amazon listings add that they are ETL listed to the 5th edition), and First Alert lists the CO710 to UL 2034.
• Power that survives an outage. CPSC recommends battery-operated CO alarms or alarms with battery backup, so every plug-in and hardwired pick carries a backup.
• An electrochemical sensor and an 85 dB horn. Every pick names its sensor type, and UL 2034 requires at least 85 decibels at 10 feet.
• A stated service life. Each pick signals when it is due for replacement, and all of them are rated for 10 years.
• Sold by Amazon itself when we checked on Nov 8, 2026, rather than by a third-party seller.

A CO alarm is step two in our guide to measuring indoor air quality at home; the other hazard that needs its own test is radon (see our best radon detectors).

What sets off a carbon monoxide alarm

UL 2034 does not use a single trigger level. It sets a time window for each concentration, based on the exposure that would raise carboxyhemoglobin (CO bound to the blood's hemoglobin) to 10 percent. CPSC staff's September 2026 memo shows the same windows in the current 5th edition.

UL 2034 alarm points (Table 41.1). Every pick on this page states these times.

CO level	What UL 2034 requires
30 ppm	No alarm for 30 days
70 ppm	Alarm within 60 to 240 minutes (no alarm in the first 60)
150 ppm	Alarm within 10 to 50 minutes
400 ppm	Alarm within 4 to 15 minutes

Three things follow. First, a listed alarm is built not to sound for a brief exposure; UL Standards & Engagement's example is lighting a gas stove. Second, a display cannot show anything below 30 ppm. UL 2034 says "No indication shall be given for CO concentrations less than 30 ppm", and CPSC staff add that a display must not read 0 either, so a blank screen means under 30 ppm, not none. Third, the standard allows an optional pre-alarm above 30 ppm, which is how Kidde's low-level models give an earlier warning.

UL 2034 also requires the instructions to say that people with medical problems may consider devices that signal CO under 30 ppm, and every Kidde data sheet repeats that line. Those are low-level CO monitors, a separate category from home alarms.

Which type goes where

From the CPSC pages and the makers' data sheets and guides cited on this page.

Type	Our pick	Works in a power cut	Good spot	Watch for
10-year sealed battery	Kidde COBD10	Yes	Hallway outside bedrooms, any wall or table	Replace the whole unit at 10 years
Plug-in with AA backup	Kidde COPD	Yes, for short outages	An unswitched outlet on each level	No switched or dimmer outlets; alkaline AAs only
AA battery only	Kidde COB	Yes	Extra levels, basement bedrooms	Batteries every year (CPSC)
Tabletop, sealed battery	First Alert CO710	Yes	Dresser or nightstand, 3 feet up or less	An extra alarm, not the hallway one
Smoke and CO combo	Kidde 30CUD10	Yes	Where a smoke alarm also belongs	Wall or ceiling, per its guide
Hardwired, interconnected	Kidde 30CUA10	Yes, on its 10-year backup	Homes wired for linked alarms	Same-brand interconnect; electrician for new wiring
Smart (Wi-Fi)	Kidde COPDLQW	Alarm yes; app alerts no	Rentals, second homes, a relative's home	Kidde says app alerts are not for life safety

Buying guide

Power: sealed battery, plug-in or hardwired

CPSC and CDC both call for battery-operated alarms or alarms with battery backup. A 10-year sealed battery is the least upkeep; plug-ins fall back on AA cells during short outages; and wired interconnection needs a hardwired alarm such as the 30CUA10, which carries its own 10-year backup.

Replace-by date and end-of-life chirps

UL 2034 requires an end-of-life signal based on the maker's stated lifetime. Kidde's alarms give theirs 10 years after they are first powered: two chirps and two amber blinks a minute, which can be hushed for 24 hours at a time and not at all after 7 days. First Alert says to replace the CO710 120 months after installation. CDC advises replacing a detector following the maker's instructions or every 5 years. Kidde's guide asks you to write the replace-by date on the label before you put the alarm up.

Interconnect and smart alerts

A CO alarm warns only where the gas reaches it, and Kidde's guide warns that an alarm outside the bedroom or on a different floor may not wake a sound sleeper. Interconnection fixes that: CPSC calls interconnected CO alarms best, and NFPA's tip sheet says to interconnect all CO alarms throughout the home "for the best protection". Wi-Fi alerts do a different job. They reach your phone, not the other alarms, and Kidde says they are not intended for life safety.

Combination smoke and CO alarms

A combo makes sense where you need both alarms anyway, such as the hallway outside the bedrooms, and it needs a listing for each job: UL 217 for smoke and UL 2034 for CO. It is not a reason to skip smoke alarms elsewhere. Kidde's CO-only guide warns that a CO alarm "is not a substitute for installing and maintaining an appropriate number of smoke alarms", because it will not sense smoke or fire.

Where to put carbon monoxide detectors

• Every level and outside sleeping areas. CPSC recommends a CO alarm on each level of the home and outside sleeping areas; NFPA says a central location outside each sleeping area and on every level.
• Not in attics or basements without a bedroom. CPSC says alarms should not go there unless the space includes a sleeping area.
• Outlet height or high on the wall. CPSC allows either; for mounting height, NFPA says to follow the maker's instructions.
• Away from cooking and heating appliances. CPSC does not recommend CO alarms in kitchens or above fuel-burning appliances. Kidde says to keep its alarms at least 6 feet from heating or cooking appliances, and UL 2034 requires instructions to say not within 5 feet of a cooking appliance.
• Not in the garage. Kidde's guide puts the garage first among places to avoid, because "products of combustion are present when you start your automobile", and First Alert's CO400 manual says not to locate one in garages, kitchens or furnace rooms.
• Within the alarm's temperature range. Kidde also rules out crawl spaces, unfinished attics and porches, where temperatures leave its 40 to 100°F range, and asks for at least 3 feet of clearance from the door of a bathroom with a tub or shower, from supply ducts and from ceiling fans.

What happened to Nest Protect

Google's help page says "Nest Protect is no longer available for sale, but is still supported", and it points US buyers to a partner device that works with Nest Protect (2nd gen) in the Google Home app: the First Alert SC5 Smart Smoke & Carbon Monoxide Alarm. If you already have Nest Protects and want new alarms that link with them, that is the model Google names. When we checked, Amazon had the SC5 only from a third-party seller. For a home without Nest Protects, the picks above cover the same jobs.

CO2 is not carbon monoxide

Carbon dioxide (CO2) is the gas people breathe out, and a CO2 monitor tells you about ventilation. Carbon monoxide (CO) comes from burning fuel, and it needs a CO alarm. A search for a "CO2 detector" often means a CO alarm, so check that the box says carbon monoxide and UL 2034. For the ventilation side, see our best CO2 monitors and why indoor CO2 is worth measuring. An ordinary air quality monitor does not detect carbon monoxide either.

What to skip

• CO2 monitors and "air quality" gadgets sold as CO protection. If the box does not say it meets UL 2034, it is not a home CO alarm.
• Alarms past their replace-by date. An end-of-life chirp means a new alarm, not a new battery.
• Plug-ins in switched or dimmer-controlled outlets. Kidde's plug-in guide rules them out.
• Lithium AA cells in Kidde's plug-ins. Kidde says not to use them.
• Relying on a CO alarm for gas leaks. UL 2034 requires CO alarm instructions to say they are not designed to detect any other gas. For natural gas or propane, use an explosive gas alarm such as Kidde's COPDLG, which Kidde says detects both.

If the alarm sounds

CPSC says never to ignore an alarming CO alarm and not to try to find the source. Its advice and Kidde's guide give the same order:

1. Get everyone outdoors to fresh air.
2. Call 911 or the fire department.
3. Do not go back in until emergency responders say you can (CPSC).
4. Have a qualified technician check fuel-burning appliances before you use them again (Kidde).

CDC lists the most common symptoms of CO poisoning as headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion. Each year more than 400 Americans die from unintentional CO poisoning not linked to fires, according to CDC. UL Standards & Engagement cites a CPSC investigation that found no alarm present in 94% of carbon monoxide deaths.