First Alert 4 Bedroom House - AC Hardwired

4 Out of 5 Good

Purchased five of these on May 1, 2024 and installed, replacing five originally installed in my home when built in 2007! It was time! However, one of these detectors started its annoying beeping in October 2025. I replaced the battery but that failed to silence it so I purchased a replacement and installed it in November 2025. I think I had a bad detector and am attempting to see if the manuafacturer will refund me per the warranty info.

Terrible products from this company

Would never recommend this company. 1. Purchased 6 CO2+Smokes from them in 2022 (manufactured Sept 22). FOUR OF THEM failed within two years at 3am. 5 chirps = "end of life." They want $7 shipping PER DEVICE to replace them. I, being curious, dismantled one of the defective alarms. IT WAS COMPLETELY CLEAN. NOT A SINGLE BIT OF DUST IN IT or anywhere on the photoelectric sensor. It was just a piece of trash. 2. Decided to purchase the product on this page. ONE of them had a dead battery. Another...

Not sure if it's working with other smoke alarms

I installed five First Alert smoke alarms OK, then discovered that I needed six. I bought this one which is very close in appearance to the other five. A problem is that I can't read the raised print on the smoke alarms which I think tell what model it is, because it's white on white, small print, very hard to see. The instructions were nearly useless, giving lots of warnings and describing WHERE to install it, but saying very little about HOW to install it. I turned off the circuit breaker ...

Out of date when purchased

Purchased in Oct. 2024. Installed shortly after. Within a few weeks, two of them have already had to have their battery replaced. Likely more will soon. Called First Alert. She had me check the manufacture date on the detector, which is Feb. 2023. So they were already a year and a half old when purchased, which I did not know at the time. She said that's why the battery is already needing replacement, and likely the others will as well. No mention from her for compensation for having to replace ...

2 of six failed with repeated false alarms

I replaced 6 of our smoke detectors with these. After 2 years, two of the units have now failed with repeated false alarms. The first one started failing in the middle of the night, which is terrifying to say the least. After the same one triggered multiple times, I ended up replacing it. Now another unit started failing and causing repeated false alarms. The units were both clean with no evidence of dust buildup or insects, and in each case there was no smoke in the house and no one cooking or...

Perfect Home Protection

[This review was collected as part of a promotion.] I, apparently, have been living under a rock, because I had no clue that smoke detectors have expiration dates! I learned that it's advisable to change them out every ten years. The First Alert 9120B Hardwired Smoke Alarm with Battery Backup smoke alarms are designed to help promote household safety, by providing an early warning of fire. This hardwired smoke detector uses an ionization smoke sensor to reliably detect smoke from hot, fast-flam...

Overly Sensitive Junk

Do you want to be alerted to a fire? Do you want to be alerted to a boiling pot of water 75 feet away from the nearest smoke detector? Do you want to be alerted if someone a mile down the road has a bonfire? Then the 9120B is the smoke detector for you! Pure and utter garbage that triggers constantly for no reason at all (yes, they are new date codes, yes they have been cleaned.)

Works well

[This review was collected as part of a promotion.] I got the 6 pack for my new house when I moved in. I got the hardwired ones since I liked the idea that they were all connected. It was pretty easy to install. Each monitor came with its own set of instructions. Since the pigtail connections were included it made it really easy to wire into my existing system. (Please note I did not wire them in myself, I have an electrician in the family). I was able to put two units on each floor of my house....

Easy Install

[This review was collected as part of a promotion.] I can only report on the installation process of these. Fortunately there has been no smoke to see if they work, although the test button does work and it is loud enough to alert you. Since I don't trust myself with electrical installs, I was able to recruit my neighbors son who is in school to become an electrician. I asked him questions while he installed them to get an idea of the process. The directions were easy to read. While it would hav...

Nice and sleek

[This review was collected as part of a promotion.] I’m living in a house that’s far larger than my previous one, so I needed to be strategic about placing smoke detectors. I want to be sure that in the event of smoke, each room has a detector close enough to catch it early. It’s great that there are 6 because i am not confident that each area of my home is safe. These aren’t as bulky as many other brands. I haven’t had a fire so I can’t speak to that, but they are otherwise great - easy to ins...