First Alert SMI100-AC, 9120B Replacement Hardwire Interconnect Smoke Alarm with Battery Backup, 1-Pack

Name: First Alert SMI100-AC, 9120B Replacement Hardwire Interconnect Smoke Alarm with Battery Backup, 1-Pack
SKU: 164458
Availability: InStock

4.7 | 16,853 ratings

Price: 21.26

Last update: 01-27-2025

About this item

First Alert's Precision Detection advanced sensing technology complies with new industry standards to reduce cooking nuisance alarms and provides early warning in the event of a home fire emergency.
Through early warning interconnect, when one alarm sounds, all compatible alarms will sound
Battery backup provides continuous protection during power outages
Alarm indicator visually identifies the unit that initiated the alarm
Quick Connect Plug included allows for easy installation with no need to rewire

Product information

Technical Details

Brand	‎FIRST ALERT
Style	‎Precision Detection
Power Source	‎Battery Powered
Color	‎White
Product Dimensions	‎5.6"D x 5.6"W x 1"H
Item Weight	‎0.6 Pounds
Alarm	‎Smoke Alarm
Sensor Type	‎Ionization
Number of Items	‎1
Manufacturer	‎Resideo
UPC	‎029054022462
Item Weight	‎9.6 ounces
Item model number	‎SMI100-AC
Size	‎1-Pack
Pattern	‎SMI100-AC
Item Package Quantity	‎1
Included Components	‎Easy Adapter Plug, 9V Alkaline Battery
Batteries Included?	‎Yes
Batteries Required?	‎Yes
Battery Cell Type	‎Alkaline

Top reviews from the United States

musicman

Exact Replacement as Expected

Reviewed in the United States on November 14, 2024

Great price and prompt delivery. If these are for replacements and your smoke detectors are old you may need to replace the bezel and the AC pigtail which are included. I replaced mine 10 years ago and that was necessary. This time these replacements fit perfectly. I still replaced the bezel because they had slightly ‘yellowed’ and it is very easy to do, just two screws. The pigtails did not need to be replaced.

I recommend replacing the installed batteries which are not even alkaline. I replaced them with Amazon Basics 9V lithium batteries which should last ten years, the life of the detectors. FYI, I got 5yrs using alkaline cells but the extra cost of lithium cells will keep me off the ladder for the life of the detectors.

Dana Smith

Great Replacements for Old Detectors

Reviewed in the United States on January 5, 2025

Very easy to install. Alarm accuracy is good. Reliability appears sufficient as they have gone off a few times after detecting a small amount of smoke while cooking, but we have not experienced any inappropriate alarms. Bright white color looks great.

A. Robinson

Easy Installation

Reviewed in the United States on December 11, 2024

I had to replace 4 smoke detectors in my mom’s home after the fire department came and checked the alarms. These were cheaper than the same brand sold in Home Depot and Lowe’s. It was very easy to install since I used the wires already installed previously. Time will tell how well they work. So far, I’m satisfied with this purchase.

Ron

Easy To Install

Reviewed in the United States on November 27, 2024

Easy to install and works great.

Grammy2012

Good price.

Reviewed in the United States on December 4, 2024

The installation of these smoke detectors was straight forward. Each one worked just fine. I would buy them again. My tiny problem was they didn’t come with screws. It’s a new build so no existing mounts. Wish I would have known to save a trip to a store when we live 30 miles from a store out in the country. But all in all a good product at a good price.

John S.

Great product.

Reviewed in the United States on October 8, 2024

Needed to replace all of the smoke detectors in my house because they were all 20 years old and starting to fail. These were super easy to swap them out with and work great!

Aisha Richards

Easy to install with little to no experience

Reviewed in the United States on January 3, 2025

I bought the six pack to replace some old and yellowing wired units in my house. As a young woman with few tools and even less experience, installation was very easy. All I had to do was unplug the old ones, put the new mount up, plug the new one in, screw it into the mount, and boom! They look much better than the 'yellowed' units removed, and as they are interconnected, all alarm when one alarms. Blinking green light and flashing red led every minute (normal operation) might be a disturbance to some in a dark room, but I have no issues. These took about 10 min per unit to replace.

Chris Dobyns

Perfect OEM Smoke Alarm Replacement

Reviewed in the United States on January 10, 2025

This a repeat purchase to replace that last of three hard-wired smoke alarms from First Alert, which finally failed after +20 years of use. The new alarm was fully compatible with the existing wiring, and only required swapping out the current installation housing. The new alarm also includes a CO2 detector, in addition to the smoke alarm sensor.

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