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🚨 Stay ahead of danger with the CO alarm that never sleeps!
The First Alert CO400 Battery Carbon Monoxide Alarm features a highly accurate electrochemical sensor with a 5-year lifespan, powered by a replaceable 9V battery for reliable, uninterrupted monitoring. Its loud 85 dB alarm ensures immediate alerts to dangerous CO levels, while easy no-install setup and smart battery/end-of-life signals provide hassle-free, continuous home safety backed by a 5-year limited warranty and UL certification.











| ASIN | B000N8OYXI |
| Alarm | Audible |
| Best Sellers Rank | #236 in Tools & Home Improvement ( See Top 100 in Tools & Home Improvement ) #4 in Carbon Monoxide Detectors |
| Brand | First Alert |
| Built-In Media | Alarm; Mounting Bracket; User Manual; 9V Battery |
| Color | White |
| Customer Reviews | 4.6 out of 5 stars 22,000 Reviews |
| Enclosure Material | Multi |
| Global Trade Identification Number | 00029054000699 |
| Item Dimensions D x W x H | 1"D x 5"W x 3"H |
| Item Highlight | CO400 |
| Item Type Name | First Alert CO400FF Battery Powered Carbon Monoxide Alarm |
| Item Weight | 11.2 ounces |
| Manufacturer | First Alert |
| Manufacturer Contact Information | 1 (800) 323-9005. |
| Manufacturer Warranty Description | 5 Year Limited Warranty |
| Mfr Part Number | CO400 |
| Model Number | CO400 |
| Number of Items | 1 |
| Operating Humidity | 10-95% RH |
| Power Source | Battery Powered |
| Product Dimensions | 1"D x 5"W x 3"H |
| Product Style | Battery Powered |
| Sensor Type | Electrochemical |
| Style | Battery Powered |
| UPC | 029054000699 |
| Unit Count | 1 Count |
J**.
Simple, reliable, and essential for home safety
I recently purchased this First Alert CO400 detector to add another layer of safety to my home, and I’m very satisfied with the experience. What I appreciate most is the straightforward, battery-operated design. It was incredibly easy to set up—no hardwiring or complex installation required, which makes it perfect for placing exactly where you need it without worrying about electrical outlets. The unit feels sturdy and well-built, and the alarm is loud and impossible to miss. It provides great peace of mind, especially given how unobtrusive and reliable it has been since I installed it. For anyone looking for a no-fuss, effective way to monitor carbon monoxide levels in their living space, this is a solid, must-have product.
B**N
Excellent 👍
We had this exact one for YEARS and it finally died on us. Got another one and it's doing its job well once again. 😁 Definitely recommend!
P**Y
for home, for travel, for car (add to winter car bag in case stuck in blizzard). 9 volt included
I purchased two packs of the pack of 2. So far so good!? Tested fine. Hope it actually works, which is why I went with a name brand. This is not the place to skimp. The C0400 carbon monoxide detector comes with a 9 volt battery. I knew I needed to replace my existing detector (they dont last forever, and need to be replaced ever so often) and I did not want the plug in style. I wanted battery operated so I could place it wherever I wanted and not be limited to available outlets. I also bought a second pack as a gift. I prefer giving practical, functional gifts, especially stuff that people tend to not want to buy, such as smoke alarms, fire extinguishers, carbon monoxide detectors. If you travel, consider a battery operated detector such as this. Dont trust that a hotel room has you covered, or someone else's house. It is small and light weight enough that it should be the thing to pack (take out battery, store separately until in room). I will likely buy an additional pack. Right now I have one on the first floor, and one outside my second floor bedroom door. I think having one in the basement and another in actual bedroom or elsewhere (spread out) would be better. Watch for sales, but if need be just buy them at any cost so you have them. I am even thinking about adding one to my winter car kit. If ever stuck in a blizzard and had to stay in my car for any length of time, having a detector will help as CO2 levels can quickly rise if running car (or if a few people are simply breathing without the window open a crack) to keep warm. Tail pipes can easily clog especially if windy. So yeh, simple thing to stay safe and alive
J**E
They don't last forever.
This is my second one of these. The first one lasted about 7 years before it started chirping and wouldn't stop. I thought it was the battery, but no, so I chucked it and bought this one. First Alert is a big name, so I trust it. Apparently, like smoke detectors, they have to be replaced every so often. The only thing I don't like about it is that there is a code for the number of chirps, and it's not printed clearly on the back, which would be nice. I have no time to look stuff up, but unless there's a problem, it's quiet.
S**N
CO alarm
works as advertised. easy to install and to hide away due to the small size. this was the cheapest i could find it so great value
C**U
Good product
2 pack is a good value. Easy installation.
C**S
Simple, reliable, and easy to install.
Installed both in under five minutes. Loud test beep, compact profile, and great price for a 2-pack. Works as advertised!
S**K
Essential safety device
Our old one timed out and alerted us. This is the direct replacement for that model that has worked very well for us for a long time. I’m very satisfied with this product.
C**K
Seems good
Quickly mounted to the wall and put batteries in. Tested. Made beep noises that split eardrums. Due to the battery nature of it it can mount anywhere close to the ground to detect CO quickly. I wont truly know if it works, and I hope I never need to, but appears solid.
F**E
Delivered eal
Came on time works well
L**N
Bonne grandeur
Grandeur exacte Bon tissu pas de la guenille
J**W
Great
Works well and worth the $$$
R**Y
A must have for every home!
Haven’t used it yet, but for the price it’s a no brainer. Carbon monoxide is a life threatening hazard and buying one or 2 of these carbon monoxide detectors is an essential for any household. I like that this is battery operated and can be placed anywhere.
Trustpilot
1 month ago
1 day ago