The Edit — Home Safety
Carbon Monoxide Detectors Compared: Plug-In to Combo
6 carbon monoxide alarms from Kidde, First Alert and X-Sense, from a plug-in with battery backup to a 5-pack of smoke and CO combos, with where each one goes and the complaint owners raise.
This guide is research-led: we have not handled these units ourselves. If you buy through our links we may earn a commission — it never changes a pick.Research-led, nothing handled. We may earn from links; it never changes a pick. How we choose
The 6 carbon monoxide alarms here are ranked by rating, then by how many owners rated them, read on 20 October 2026, as How we choose describes. 4 detect carbon monoxide alone and 2 are smoke and CO combos, and each listing’s power source sits beside what owners report about reliability and battery life. Nothing here was handled or tested.
Best for Most homes: outlet plus backup
Watch for Needs an outlet in the right spot
Best for Seeing the CO level
Watch for Batteries to change
Best for A plain alarm per level
Watch for Some last about 1.5 years
Best for Travel and rentals
Watch for Newer listing
Best for Smoke and CO everywhere at once
Watch for Some malfunctions reported
Best for One combo for one hallway
Watch for Grating warning beeps
CPSC wants a CO alarm on every level, outside the bedrooms
The US Consumer Product Safety Commission says to install CO alarms that run on batteries, or have battery backup, on every level of the home and outside sleeping areas. For a 2-storey house with a basement bedroom, that is 3 alarms. Carbon monoxide has no smell or colour, and CPSC lists headache, dizziness, weakness, nausea, vomiting, sleepiness and confusion as its symptoms, which is why an alarm outside the bedroom matters most at night.
Kidde’s plug-in keeps working in a power cut
The Kidde plug-in alarm plugs into a wall outlet and carries AA batteries as backup, with an 85 dB horn and LED status lights, per the listing. It rates 4.8 across 1,308 ratings, the highest here. Owners call it reliable and simple, value its 10-year life and the backup batteries, and say it is worth the price. No complaint recurs. The catch is placement: it needs an outlet in the hallway outside the bedrooms.
Kidde Carbon Monoxide Detector, Plug-in with AA Battery Backup, 85 dB Alarm
Plugs into a wall outlet, with AA batteries to keep it working when the power goes out.
Current price shown on Amazon. We may earn a commission.
| Power | Plug-in, AA battery backup |
|---|---|
| Alarm | 85 dB |
Owners like that it simply plugs in, with batteries as backup, and trust it to last 10 years.
Buy it if
- One per level, in an outlet near the bedrooms
Don't buy it if
- A hallway with no outlet where the alarm should go
Kidde’s battery alarm shows the CO level
The Kidde battery CO alarm runs on AA batteries and, owners report, shows the actual carbon monoxide level on a clear digital display. It rates 4.7 across 19,928 ratings. Owners find it reliable and quick to install, and like that it runs on standard batteries. No complaint recurs. A reading helps tell a low, lingering level from a sudden spike, which a plain horn cannot.
Kidde Carbon Monoxide Detector, AA Battery Powered CO Alarm with LEDs
A battery CO alarm that owners say shows the actual CO level on a clear display.
Current price shown on Amazon. We may earn a commission.
| Power | AA batteries |
|---|---|
| Display | CO level, per owners |
Owners like the display of the CO level and the quick install on AA batteries.
Buy it if
- Anyone who wants to see a number, not just hear a horn
Don't buy it if
- Anyone who will not change batteries
First Alert CO400 has the deepest owner record
The First Alert CO400 is a battery CO alarm that rates 4.6 across 22,082 ratings, the most on this page. Owners treat it as an essential, call it easy to install, and some credit it with saving their lives. Battery life divides them, and some report a unit lasting only about 1.5 years. Press its test button monthly, as CPSC advises for every alarm.
First Alert Battery Carbon Monoxide Alarm, CO400
A battery CO alarm with the most owner ratings here, which snaps onto its base.
Current price shown on Amazon. We may earn a commission.
| Power | Battery |
|---|
Owners trust it and find it easy to fit. Some report it lasting about 1.5 years.
Buy it if
- A plain alarm for each level, from a familiar maker
Don't buy it if
- A long service life, as some owners report about 1.5 years
Kidde COB is small enough to pack
The Kidde COB is a compact AA-powered CO alarm with an 85 dB horn, per the listing. It rates 4.6 across 391 ratings, a newer listing with fewer reviews yet. Owners like the small size and take it on trips, to hotels and rentals with gas heat. They call it easy to set up and good value. A vacation rental’s alarm is somebody else’s maintenance, which is the case for carrying your own.
Kidde Carbon Monoxide Detector, AA Battery-Powered, COB
A compact AA-powered CO alarm that owners pack for hotels and rentals.
Current price shown on Amazon. We may earn a commission.
| Power | AA batteries |
|---|---|
| Alarm | 85 dB, per the listing |
Owners like the compact size and pack it for travel. Easy to set up and good value.
Buy it if
- A suitcase, a cabin rental or a dorm room
Don't buy it if
- Anyone wanting a long owner record, as it is newer
X-Sense combos add CO to every smoke alarm
The X-Sense SC07 is a smoke and CO combo on a sealed 10-year battery, sold as a 5-pack, and rates 4.5 across 4,341 ratings. Owners find it easy to install and good-looking, and like that it measures CO levels. Reliability and value divide them, with some reporting malfunctions. The single X-Sense SC01 is the same idea in 1 unit and rates 4.5 across 2,690 ratings. Owners call it reliable and loud, though some find its warning beeps maddening. For smoke-only, interconnected and smart alarms, see smoke alarms compared.
X-Sense Smoke Detector Carbon Monoxide Detector Combo, SC07, 5-Pack
5 smoke and CO alarms on sealed 10-year batteries, not hardwired.
Current price shown on Amazon. We may earn a commission.
| Detects | Smoke and carbon monoxide |
|---|---|
| Power | Sealed 10-year battery |
| Pack | 5 alarms |
Owners like the easy install and the CO reading. Some report units malfunctioning.
Buy it if
- Replacing every smoke alarm and adding CO in one purchase
Don't buy it if
- Reliability, as some owners report malfunctions
X-Sense Smoke Detector and Carbon Monoxide Detector, SC01, 1-Pack
One smoke and CO alarm on a sealed 10-year battery, not hardwired.
Current price shown on Amazon. We may earn a commission.
| Detects | Smoke and carbon monoxide |
|---|---|
| Power | Sealed 10-year battery |
Owners call it reliable and loud, and like the 10-year battery. Some find the beeping maddening.
Buy it if
- A single bedroom hallway that needs both alarms
Don't buy it if
- Light sleepers, as some find its warning beeps maddening
What did not make the list
The Siterwell CO alarm rates 4.6 across 210 ratings and is sold on a 7-year product life, but owners note its batteries are not 10-year batteries, so it still needs changes the sealed alarms avoid. The hardwired Kidde combo for replacing an old ceiling alarm is in the Kidde hardwired profile.
Prices, savings and deal badges are Amazon's own, read from Amazon within the last hour. Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product.
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Kidde Carbon Monoxide Detector, Plug-in with AA Battery Backup, 85 dB Alarm