BRK First Alert 9120BFF/ SMI100-AC Smoke Detector, Hardwired Alarm with Battery Backup, White, 1-Pack

I got this to replace a smoke detector, which was acting up and this worked perfect. The price was great. Installation was easy. Connected simply. Works great. Matches the one I was replacing. Piece of cake! Noise/alarm is loud. Peace of mind is back. Pleased w this replacement.

Exact one that I was replacing. Simply plug and play. Worked perfectly.

I needed to replace a First Alert model 9120B: it started to chirp because the battery was low. When I removed it from the ceiling I saw that it was over ten years old. I read that smoke detectors should be replaced at that age. I wanted an identical replacement so it would fit on the same mounting bracket in my ceiling and use the same power connector that's connected to AC power in the ceiling. I saw this model, 9120BFF, and the photos on the Amazon page show the unit labelled 9120B despite the "FF" at the end of the model number in the product description. I wasn't sure if it was the same, so I tried searching for model 9120BFF, but all I found was the same page on Amazon. But I ordered it anyway, and it is indeed the First Alert model 9120B. It is an exact replacement and works great. It fits on the same mounting bracket and uses the same power connector that my old smoke detector used. It comes with a new mounting bracket and power connector, which I don't need. And it comes with a new 9V battery: there's a plastic tab covering the battery terminals so no power is drawn until you pull the tab out of the unit when you install it. So why is this called model 9120BFF instead of 9120B? I think it's the packaging: see the picture attached. It comes in a plain corrugated box, which I assume is how they sell it to contractors. It's not in consumer packaging with a glossy cover like you'd find in a retail hardware store. But it's the same product: the label on the unit says Model 9120B, and it comes with instructions for that model. There's one other clue that it is sold to contractors: it includes a plastic dust cover that looks like a miniature shower cap. The dust cover is to be used during construction to keep dust out of the unit; you remove it when construction is finished. (It could be that the dust cover is also in the consumer version; I'm just guessing here.) Anyway, I'm happy with the purchase: it didn't require any ceiling work to replace my old smoke detector, which was my goal.

I bought this as a replacement for one that was at end of life (Lasted 8 years). Easy to install and works great! I did not notice it was not carbon monoxide detector also. So make sure you check that if you want to monitor both smoke and Carbon Monoxide. Other then that, it fits on the same bracket as my old model SC9120B that is obsolete. Uses the same 120vac connector as the old. Interconnects with the my other 4 original monitors that still work. So if you have one that is NG, (my old one, chirped 3 times every 5 minutes or so even after cleaning and replacing battery) you can just replace that one and be OK.

The BRK First Alert is the parent company of First Alert making this alarm just as good as the more expensive First Alert smoke alarms. They're easy to install, they can be wired in series so if one goes off they all go off or independently. I purchased 3 of them and I'm quite satisfied with them.

This smoke alarm has a 10-year lifespan but after I ordered them I read horror stories of stale supplies being sold. The lifespan is not from the time of installation. It is from the date of manufacturing. So they could ship stale ones from a couple years ago and still be okay. These were ordered in September and made in June 2026. They all worked perfectly. They all fit the old brackets. When installing, shut off power to the unit; be sure to remove the plastic tab to activate the battery, and then turn the power back on. This will eliminate beeping from the unit self-programming that it is missing a battery if you turn power on and then remove plastic tab to activate battery.

This is a well made smoke detector. We bought one to replace the original smoke detector from when the house was built. The old one was chirping like tweety bird at 3am, and wouldn’t stop. My husband has no handyman skills so he took a hammer to it until it died. He installed this unit when received and it was easy to install. We ordered 2 more to replace the others before they start chirping.

Works and looks good

We bought this to replace our expired smoke detector. It was easy to install and it fit the base that was already mounted on our ceiling. This avoided removing a base and damaging paint, just to install a new base.

Works good so far :)

Rapport qualité / prix

These were easy to install, given that my First Alert smoke detectors had given it up after only one year of use. These were installed to replace the two that died, and they were throw aways ( which I really disliked). These ones have a drawer for a backup battery which is the way to go. Hopefully they perform well. So far so good. But the proof is in the performance

Great value easy setup