First Alert CO400 Carbon Monoxide (CO) Detector, Battery Operated Alarm, 1-Pack
4.6 | 22,401 ratings
Price: 19.99
Last update: 01-28-2026
About this item
- Keep your family safe with this easy to use, battery operated carbon monoxide alarm; Battery powered alarms provide continuous monitoring of CO levels, even if there's a power failure
- Features an advanced electrochemical carbon monoxide sensor that accurately detects carbon monoxide levels, no matter where the detector is placed in the room.The alarm sequence should last 5-6 seconds. If it does not alarm, make sure fresh batteries are correctly installed, and test it again. If the unit still does not alarm, replace it immediately
- A loud 85 decibel alarm sounds when CO levels reach dangerous , Battery Replaceable - Yes
- To ensure complete protection make sure to place one on each level of your home and in each bedroom
- 5-year limited warranty; Equipped with end of life signal chirp, so you know when it’s time to replace the unit for safety
- All first alert CO alarms are rigorously tested to meet UL standards
- First Alert has been the most trusted brand in home safety since launching the first residential smoke alarm in 1958 (Based on a First Alert Brand Trust Survey in February 2018)
Product information
Features & Specs
| Power Source | Battery Powered |
|---|---|
| Alarm | Audible |
| Sensor Type | Electrochemical |
User guide
| Operating Humidity | 10-95% RH |
|---|
Style
| Product Style | Battery Powered |
|---|---|
| Color | White |
Measurements
| Item Dimensions D x W x H | 1"D x 5"W x 3"H |
|---|---|
| Item Weight | 0.45 Pounds |
Additional details
| Enclosure Material | Multi |
|---|
Warranty & Support
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First Alert CO400 Carbon Monoxide (CO) Detector, Battery Operated Alarm, 1-Pack
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Item details
| Brand | First Alert |
|---|---|
| Model Number | CO400 |
| Global Trade Identification Number | 00029054000699 |
| Manufacturer | First Alert |
| UPC | 029054000699 |
| Customer Reviews | 4.64.6 out of 5 stars(22,382) 4.6 out of 5 stars |
| Best Sellers Rank |
|
| ASIN | B000N8OYXI |
| Item Type Name | First Alert CO400FF Battery Powered Carbon Monoxide Alarm |
| Built-In Media | Alarm; Mounting Bracket; User Manual; 9V Battery |
| Item Height | 3 inches |
| Manufacturer Contact Information | 1 (800) 323-9005. |
| Unit Count | 1.0 Count |
| Manufacturer Warranty Description | 5 Year Limited Warranty |
Top reviews from the United States
- StevenGreat Carbon Monoxide Detector – Easy to Install and Reliable!I bought two of the First Alert Carbon Monoxide Detectors (model CO400), and I’m very happy with them. They were super easy to install — no outlet needed since they run on batteries. I just mounted them on the wall, and they were ready to go in minutes.I like that the battery operation means I can place them anywhere in my home without worrying about finding a plug. The alarm is loud enough to hear clearly, and the design is compact and simple.It gives me peace of mind knowing my family is protected. Overall, great value, easy setup, and reliable safety product. Highly recommend!
- Martha PhelpsGreat deal for the price.Works great, looks good. Definitely recommend. Great deal for the price.
- Ava CampbellGreat value, easy installation, good qualityI was able to easily mount it to my wall. Seems reliable, glad it comes with batteries. Price is reasonable! Alarm sound is super loud and it’s easy to test. Overall I’m satisfied and I’m glad I made this purchase. I feel secure knowing this is in my house.
- druznakEasy to installWork great but was to replace two that stopped functioning and never game any sort of warning beep. Hopefully these do a better job.
- Blanca M.Work very goodGood quality product
- Alan A DevernoeBrand name. Easy to install.Easy to install.
- Bobby DExcellent Safety ProductExcellent value for a great product.
- Verified PurchaserGet a good battery!I bought this one to replace an eight year old unit that was essentially the same. It’s great, with only one minor problem. The cheap battery included in the packaging started the low battery warning chirp immediately. Spend a couple more dollars and get a quality 9v. Throw the included battery away.