BRK SC9120B-3 Hardwired Smoke and Carbon Monoxide (CO) Detector with Battery Backup, White, Pack of 3

I recently installed the First Alert Combination Smoke & Carbon Monoxide Alarm (SMICO100-AC), and I’m very pleased with its performance. Installation was straightforward — the hardwired setup with battery backup provides peace of mind knowing it stays powered even if the electricity goes out. This alarm detects both smoke and carbon monoxide, which gives me confidence that my home is protected on multiple levels with just one device. It’s loud and responsive during testing, and the included battery backup is a great safety feature. The interconnect capability is excellent too — when one alarm sounds, all interconnected units activate, which is ideal for larger homes. Overall, this feels like a high-quality product from a trusted brand. Easy to install, dependable, and a smart investment in home safety. Highly recommend!

I have been a master electrician for 32+ years. If you're not 100% sure of what you're doing, hire a professional! Ok a lot of people are complaining about the new connector. It literally takes 60 seconds to rewire. I rewire anyways so I can put a meter on the ceiling wires to make sure everything is as it should be. The base is a tad smaller than my previous ones. They were from a different company though. It presented zero issues during the installation. I have 3 detectors upstairs and one in the basement. I wired them all and they all worked inline perfectly. When one goes off, they all go off. The alarm is very loud and high pitched. It also tests both the smoke and CO² detectors when pushing the test button. You'll get a beep and then another beep. Then it repeats. Meaning they are all working. Bonus each detector comes with a pre installed Duracell 9 volt battery. You also receive a dust cover for the detector if you need to work in that room. Kicking up dust or debris can get inside the unit and fault it. Nice little freebie to have. Although I didn't need, they come with very detailed instructions with diagrams. After I installed them all I tested it my way using certain techniques to get both detectors to alert. They passed on both smoke and CO². For this price point, I am very happy with these units. It gives me a sense of security knowing my family is protected. Please mark the back of your detectors with the date you install them. I use a black marker. Also be sure you were shipped the correct units. It should say on the outside label Combination Smoke/Carbon Monoxide Alarm. I've posted pictures along with a video. I hope this aids with your decision whether these are for your home or not. I will update again if I have any issues in the future. As of now they are working as they should and I again, am very happy with my purchase.

Easy installation especially if you already had a previous alarm in same spot. Even came with a Duracell battery backup, no junk. Good buy in my opinion.

While First Alert lists SMICO100-AC as direct replacement for the discontinued 9120B, it is NOT the same size and will NOT fit existing 9120B mounting rings. While they appear to be the same, the newer model is (strangely) a fraction of an inch larger around. Changing mounting rings is easy, but will be required. The new mounting rings are larger inner diameter, smaller outer diameter, so will not cover ceiling covered by the older mount. Plug is compatible and units appear to work as advertised. This would easily have been 5 star, I have NO idea why they didn't make the mounting match!

We recently installed the First Alert Combination Smoke & Carbon Monoxide Alarm, Interconnect Hardwire Detector, and we are extremely pleased with the decision. This unit is an outstanding choice for anyone looking to upgrade their home safety system, combining two essential protections into one convenient device. Top Features We Appreciated Dual Protection for Ultimate Peace of Mind: The biggest win here is having both smoke and carbon monoxide (CO) monitoring in a single unit. It gives great peace of mind knowing that the home is covered for two of the most critical household threats. It simplifies maintenance and ensures comprehensive safety. Seamless System Integration: A major selling point for us was its compatibility with our existing setup. This First Alert detector fit perfectly into our previous interconnected system (hardwired). The installation was straightforward, and it immediately linked up with the other alarms in the house, ensuring that if one goes off, they all do. This interconnectivity is vital for alerting everyone, no matter where they are in the house. Reliable Brand: First Alert is a name synonymous with home safety, and the quality of the unit feels robust and reliable. Conclusion If you are looking to replace old, separate smoke and CO alarms, or if you simply need to upgrade to a hardwired, interconnected system, this combination alarm is a superb choice. It delivers on its promise of simplifying safety while maximizing protection. Highly recommended!

This replacement detector was easy to install and works perfectly.

Easy to install.

Seems to work fine.

All three of our alarms gave the warning beeps within days of one another. They were finishing warranty also. I was glad to find these with three alarms. Many I had interest in were in two only. Then I’d need two pkgs with an extra one not needed. Others way beyond our senior budget. These arrived on time, safely packed and exactly as described. Our son got them up quickly and easily and we’ve had no trouble with them at all. We recommend them.

good quality, as described, easy hookup

Great price easy installation

Our older model of these were about 8 years old and didn’t have the replaceable battery so when they started beeping randomly here and there, we had no options but to change it up. It is nice how easy these are to replace for a hardwired option when the mounts are the same. This was the best place to buy them cost wise.