First Alert CO400 Carbon Monoxide (CO) Detector, Battery Operated Alarm, 1-Pack

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.

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!

I did see some negative reviews but I purchased this for the second time because I did not have any issues. The last one was reliable. Lasted over 10 years and the only chirp was end of life 5 chirps and replace battery. We are very comfortable this is doing its job!

I can't believe the prices on CO detectors!!! They are unnecessarily expensive. My current unit was over 10 years old and kept throwing error codes so it was time for a replacement. I ultimately decided on this First Alert as it is the same brand I have trusted for years. The price was affordable. I cannot attest to any longevity or functionality because an emergency has not come up. The "Test" button does work as expected.

Great product lots of instructions easy to install

I always pack a compact carbon monoxide detector when I travel—it’s small enough to slip into my luggage without a second thought, but the peace of mind it provides is huge. Whether I’m staying in a hotel or an Airbnb, it’s reassuring to know I have an extra layer of safety in an unfamiliar space. It’s one of those tiny items that takes up almost no room, yet feels absolutely essential once you start bringing it along.

Easy to set up. This was a normal replacement (I didn’t know they wear out after 5-6 years), so I just had to insert the battery that came with it and re-hang it on the existing screws. It did come with screws, but I just used the ones from the old one.

Bought on recommendation of fire department.

I purchased this alarm to install in the upstairs hallway between bedrooms. It was very easy to install and works perfectly and provides the added security I required. I was surprised and happy at how quickly the parcel arrived!

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.

This unit is very similar to the one we had for over 15 years. CO2 is a danger & we now feel safe again with the new alarm in place. The unit is just a simple plug in, but we did have to read up on where to put it. Placing it correctly is important so study up & get it right.

J’espère ne jamais l’entendre m’indiquer que nos vies sont en danger. Pour le reste tout sembke parfait...

Easy to set up, easy to use, literally something you have to have in your home.