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RateLab Home Improvement & Tools Carbon Monoxide Detectors

Best Carbon Monoxide Detectors

Updated

We compared five carbon monoxide alarms from Kidde, First Alert and Google using the makers' own spec sheets, product pages and support notes, plus the U.S. Consumer Product Safety Commission recall database. We found no recalls for any of these models as of October 2026. The specs below are the manufacturers' claims, and each review says which maker said what. We did not run our own CO tests.

The first decision is power. A plug-in alarm runs off an outlet and needs a backup battery for outages; some use replaceable AA or 9V batteries, others a sealed battery that lasts the life of the alarm. A battery-only alarm can go anywhere, including rooms with no free outlet, but the whole unit is replaced when its sealed battery runs out. Sealed batteries remove a common failure, a dead or missing backup battery, which is why they are worth paying a little more for.

The second decision is information. Every alarm here sounds at dangerous levels, but a digital display shows the CO level in parts per million, and a peak memory shows the highest level since the last reset, which helps you tell a one-off spike from a slow leak. All CO alarms wear out, and every alarm here has an end-of-life signal. Kidde and Google rate theirs for 10 years, and First Alert rates the CO710 for up to 10. Check the manufacture date when the alarm arrives, because the clock starts at the factory, not when you buy it.

Quick picks

Use this table for the fastest answer, or jump into the full review cards below.

Pick Best for Verdict Review
Best OverallKidde KN-COP-DP-10YL Most homes that want one plug-in alarm per level with no battery upkeep, Buyers who want to see the actual CO level, not just an alarm Buy Read review
Best Battery-OnlyFirst Alert CO710 Bedrooms and hallways with no free outlet near breathing height, Renters who can't mount anything on the walls Buy Read review
Plug-In With a CordFirst Alert CO615 Rooms where the only outlet is low or hidden but a shelf is close by, Buyers who want a CO readout and are fine changing AA batteries Consider Read review
Basic Budget OptionFirst Alert CO605 Adding an alarm to every level or sleeping area on a tight budget, A backup alarm next to a display model elsewhere in the house Consider Read review
Smart Combo, DiscontinuedGoogle Nest Protect Google Home households adding to an existing set of Nest Protects, Buyers who want phone alerts for smoke and CO while away from home Consider Read review

Best Overall

Best Overall

Kidde KN-COP-DP-10YL Plug-In Carbon Monoxide Alarm with 10-Year Battery Backup

The Kidde KN-COP-DP-10YL plugs into a standard outlet and keeps working through outages on a sealed lithium battery that Kidde says lasts the 10-year life of the alarm. It shows the CO level in parts per million, remembers the peak reading, and is listed to UL 2034. It is the most complete plug-in in this comparison.

Buy
TL;DR

Sealed 10-year lithium backup battery, no battery changes (Kidde)

Pros

  • Sealed backup battery removes a common failure, a dead or missing backup battery
  • PPM readout and peak memory make low or intermittent CO easier to spot
  • Rotating plug keeps the alarm upright on vertical or horizontal outlets
  • 10-year limited warranty, longer than the 7 years First Alert gives the CO615

Cons

  • Plugs straight into the wall with no cord, so placement depends on where your outlets are
  • The display turns off during a power outage to save the battery; the alarm still works
  • No interconnect and no smart features
Verdict: Buy Full Review Check current price

Best Battery-Only Alarm

Best Battery-Only

First Alert CO710 Carbon Monoxide Alarm with 10-Year Battery and Digital Temperature Display

The First Alert CO710 needs no outlet and no installation: it sits on a table, dresser or shelf and runs on a sealed lithium battery First Alert rates for up to 10 years. Its backlit display shows the current CO level, recent peak levels or the room temperature, and it signals when the alarm reaches end of life.

Buy
TL;DR

Sealed 10-year lithium battery, cannot be removed (First Alert)

Pros

  • No outlet, wiring or wall mount needed, so it can sit wherever the risk is
  • Sealed battery means no battery changes over the life of the alarm
  • Shows current CO, recent peaks and room temperature on one display

Cons

  • Designed to sit on a surface, so it can be moved, covered or knocked off
  • When the sealed battery reaches end of life, the whole alarm is replaced
  • No interconnect and no smart features
Verdict: Buy Full Review Check current price

Plug-In With a Cord

Plug-In With a Cord

First Alert CO615 Plug-In Carbon Monoxide Alarm with Battery Backup and Digital Display

The First Alert CO615 plugs in with a 6-foot cord, so it can sit on a shelf instead of hanging off a low outlet. It has a backlit digital display, an 85 dB alarm and two AA backup batteries. First Alert gives it a 7-year limited warranty and no longer sells it on its own store.

Consider
TL;DR

6-foot power cord for shelf or tabletop placement

Pros

  • The 6-foot cord gives more placement choice than a direct plug-in
  • Backlit display shows the CO level at a glance
  • Low-battery indicator and alarm warn you when the backup needs new batteries

Cons

  • AA backup batteries need replacing, and a dead backup means no protection in an outage
  • 7-year limited warranty, shorter than the 10 years Kidde gives the KN-COP-DP-10YL
  • First Alert's own store lists it as no longer available for sale, so stock may thin out
  • First Alert's product page does not list peak memory for this model
Verdict: Consider Full Review Check current price

Basic Budget Option

Basic Budget Option

First Alert CO605 Plug-In Carbon Monoxide Alarm with Battery Backup

The First Alert CO605 is the simplest alarm here: it plugs into an outlet, keeps running on a backup battery during outages, and gives low-battery and end-of-life warnings. It has no display, so you only learn about CO when the alarm sounds. A sensible way to add coverage to more rooms on a tight budget.

Consider
TL;DR

Plug-in with battery backup for power outages

Pros

  • Budget-friendly way to cover more rooms
  • Battery backup keeps it working during outages
  • Low-battery and end-of-life warnings

Cons

  • No display, so low CO that stays under the alarm level is invisible to you
  • Replaceable backup battery; First Alert recommends changing it at least twice a year
  • Listings differ on the backup battery type between variants, so check the package
Verdict: Consider Full Review Check current price

Smart Combo, Discontinued

Smart Combo, Discontinued

Google Nest Protect Smoke and Carbon Monoxide Alarm (Battery, 2nd Gen)

The Google Nest Protect detects smoke and carbon monoxide, speaks its warnings and sends alerts to your phone when you're away. Google stopped making it in 2025 and sold remaining stock while it lasted. Google says existing units keep working and receive updates until they expire, 10 years after their manufacture date.

Consider
TL;DR

Smoke and CO alarm in one unit, battery powered

Pros

  • Only alarm here that sends smoke and CO alerts to your phone
  • Spoken warnings instead of only beeping
  • Covers smoke and CO in one device

Cons

  • Discontinued by Google in 2025; new stock is whatever is left
  • Its 10-year life counts from manufacture, so a unit that sat in a warehouse has less time left
  • Expiry reminders in the app only work if the alarm is on Wi-Fi and set up in the app
Verdict: Consider Full Review Check current price

All Carbon Monoxide Detectors reviews

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Tools / Carbon Monoxide Detectors Consider

First Alert CO605 Plug-In Carbon Monoxide Alarm with Battery Backup

The First Alert CO605 is the simplest alarm here: it plugs into an outlet, keeps running on a backup battery during outages, and gives low-battery and end-of-life warnings. It has no display, so you only learn about CO when the alarm sounds. A sensible way to add coverage to more rooms on a tight budget.

Read review →
Tools / Carbon Monoxide Detectors Consider

Google Nest Protect Smoke and Carbon Monoxide Alarm (Battery, 2nd Gen)

The Google Nest Protect detects smoke and carbon monoxide, speaks its warnings and sends alerts to your phone when you're away. Google stopped making it in 2025 and sold remaining stock while it lasted. Google says existing units keep working and receive updates until they expire, 10 years after their manufacture date.

Read review →

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