What a silent alarm does and does not prove
The 5 highest scores among the 11 CO alarms we cover that have a checked Amazon.com listing. Scores are out of ten and only compare models inside this category.
| # | Model | Our score | Price | Buy |
|---|---|---|---|---|
| 1 | Kidde KN-COB-LP2 Battery CO AlarmBest for: A cabin or travel alarm, or a second alarm at home. | 8.5/10 | ≈ $25 | Check price on Amazon: Kidde KN-COB-LP2 Battery CO Alarm |
| 2 | Kidde KN-COPP-3 Plug-In CO Alarm with DisplayBest for: A buyer who trusts a long record over a newer model. | 8.5/10 | ≈ $70 | Check price on Amazon: Kidde KN-COPP-3 Plug-In CO Alarm with Display |
| 3 | Kidde COPD Plug-In CO Alarm with DisplayBest for: A bedroom or a stove room with a convenient outlet. | 8.4/10 | ≈ $44 | Check price on Amazon: Kidde COPD Plug-In CO Alarm with Display |
| 4 | First Alert CO400 Battery CO AlarmBest for: A second alarm near a stove or in a bedroom, on a budget. | 8.3/10 | ≈ $22 | Check price on Amazon: First Alert CO400 Battery CO Alarm |
| 5 | First Alert CO605 Plug-In CO Alarm, 3-PackBest for: Covering each level and bedroom at once. | 8.3/10 | ≈ $71 | Check price on Amazon: First Alert CO605 Plug-In CO Alarm, 3-Pack |
Prices are indicative and were read on Amazon.com; the button shows the current one. If we earn a commission, it does not change the order.
Every home CO alarm answers to UL 2034, which sets how long it may wait at each level. It must stay quiet below 30 ppm, so a slowly spilling stove may never set one off. That is why a display model makes sense in a room with a wood stove, as it can show a reading no alarm would sound for.
2 AA batteries · electrochemical · 85 dB · LEDs · Event Memory · portable
A small AA alarm with Event Memory, which records the last time it detected CO, with 2,356 ratings at 4.7 out of 5.
Best for: A cabin or travel alarm, or a second alarm at home.
≈ $25
9V battery · electrochemical sensor · 7.2 oz · 10 to 95% RH
The default CO alarm: a simple 9V battery model with 22,134 ratings at 4.6 out of 5, with almost nothing written on the listing.
Best for: A second alarm near a stove or in a bedroom, on a budget.
≈ $22
AA battery · UL 2034 5th Edition stated · ETL listed · 85 dB · test/hush · 10-year limited warranty
The newer Kidde alarm, which names the UL 2034 5th Edition and carries a 10-year limited warranty.
Best for: A buyer who wants the standard named in writing.
≈ $25
plug-in · 10-year battery backup · foldable plug · electrochemical · travel size
A foldable plug-in detector with a 10-year backup battery, small enough for travel.
Best for: Travel, or a low-cost spare.
≈ $27
plug-in · 2 AA backup · backlit display · 85 dB · UL 2034 5th Edition stated · rotating plug
A plug-in alarm with a CO display, a rotating plug and AA backup, naming UL 2034 5th Edition.
Best for: A bedroom or a stove room with a convenient outlet.
≈ $44
10-year battery · backlit display · shows CO and temperature · 85 dB · 6.4 oz
A sealed 10-year alarm with a backlit digital display, the kind of model to put near a stove.
Best for: The alarm nearest a wood stove, where you want to see a number.
≈ $44
smoke and CO · Precision Detection · battery · end-of-life warning · test/silence button
One unit for smoke and CO, with First Alert’s Precision Detection to reduce cooking false alarms.
Best for: A hallway where one combined alarm is the practical choice.
≈ $37
10-year sealed battery · photoelectric smoke · electrochemical CO · LCD · UL 217 and UL 2034 stated
A 10-year combination alarm with an LCD, naming both UL 217 and UL 2034, the same price as First Alert’s battery combo.
Best for: A single unit for a hallway outside the bedrooms.
≈ $37
plug-in · 9V backup · digital display · 85 dB · 3rd edition
The older Kidde plug-in with a digital display, a 9V backup and 28,356 ratings at 4.7 out of 5.
Best for: A buyer who trusts a long record over a newer model.
≈ $70
plug-in · 9V backup · 85 dB · electrochemical · 3-pack · 7-year limited warranty
A 3-pack of plug-in alarms with 9V backup and a 7-year warranty, which covers a whole floor plan.
Best for: Covering each level and bedroom at once.
≈ $71
LCD · 2 AA · 7-year life · ETL standards stated · 3-year warranty · 13.44 oz
A display alarm with a 7-year life and 3-year warranty, from a less known brand, with 212 ratings at 4.6 out of 5.
Best for: A buyer who finds it on sale.
≈ $50
States UL 2034 5th Edition and a 10-year limited warranty.
Three plug-in alarms with battery backup.
Follow the manual and local code. The usual advice is one on each level and near sleeping areas.
Check the date on the unit. Most makers state 7 to 10 years.
Get everyone outside to fresh air, and call 911 or the fire department from there.
Fit more than one. Use a display model near the stove, replace on date, and never assume silence means no CO.
The column appears only if four appliances in five state the value. A half-empty column separates nobody.
| Model | Price | Power | Sensor |
|---|---|---|---|
| First Alert CO400 Battery CO Alarm | $22 | 9V battery, included | Electrochemical |
| Kidde COB Battery CO Alarm | $25 | AA batteries, included | Electrochemical |
| Kidde KN-COB-LP2 Battery CO Alarm | $25 | 2 AA batteries, included | Electrochemical |
| Siterlink A4602A Plug-In CO Detector | $27 | AC plug-in, 10-year battery backup | Electrochemical |
| First Alert SMICO100 Smoke and CO Alarm | $37 | Battery | Ionization in the table |
| X-Sense SC07 Smoke and CO Alarm | $37 | 10-year sealed lithium | — |
| First Alert CO710 10-Year CO Alarm with Display | $44 | Built-in 10-year battery | Electrochemical |
| Kidde COPD Plug-In CO Alarm with Display | $44 | 120V plug-in, 2 AA backup | — |
| SITERWELL GS828A CO Detector | $50 | 2 AA batteries, built in | Electrochemical |
| Kidde KN-COPP-3 Plug-In CO Alarm with Display | $70 | Plug-in, 9V backup | Ionization in the table, which looks like an error |
| First Alert CO605 Plug-In CO Alarm, 3-Pack | $71 | Plug-in, 9V backup | Electrochemical |
$22 – $25
3 models
First Alert CO400 Battery CO Alarm, Kidde COB Battery CO Alarm, Kidde KN-COB-LP2 Battery CO Alarm
$27 – $37
3 models
Siterlink A4602A Plug-In CO Detector, First Alert SMICO100 Smoke and CO Alarm, X-Sense SC07 Smoke and CO Alarm
$44 – $71
5 models
First Alert CO710 10-Year CO Alarm with Display, Kidde COPD Plug-In CO Alarm with Display, SITERWELL GS828A CO Detector
Specifications: manufacturer sheets for wood heating equipment and the matching Amazon product pages. Prices and availability: read on Amazon.com from a New York address. Every figure in this table names its source.
Most recent revision in this category: November 14, 2026.
The price beside each product is fetched as this page opens, and it is the only figure here that is current. Any amount written into the prose was read once, on the day that sentence was written, and nothing has refreshed it since.
