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First Alert

First Alert SMI100, Battery-Operated Smoke Alarm, 2-Pack

  • Based on 24,746 reviews
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Availability: In Stock.
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Arrives Sunday, Mar 22
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Size: 2-Pack


Style: Precision Detection


Pattern Name: SMI100


Features

  • 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
  • Battery-operated alarm allows for easy installation and maintenance
  • Front access battery compartment makes for easy battery replacements
  • End-of-life warning lets you know when its time to replace the alarm
  • Test/silence button for efficient testing to ensure alarm is working properly

Description

The First Alert SMI100 Battery-Operated Smoke Alarm is equipped with First Alert's Precision Detection advanced sensing technology and meets new industry standards. This battery-operated smoke alarm is easy to install and the front access battery compartment makes for easy battery replacements.

Brand: First Alert


Style: Precision Detection


Power Source: Battery Powered


Color: White


Item Weight: 0.6 Pounds


Alarm: Smoke


Sensor Type: Ionization


Number of Items: 2


Manufacturer: Resideo


UPC:


Brand: ‎First Alert


Style: ‎Precision Detection


Power Source: ‎Battery Powered


Color: ‎White


Item Weight: ‎0.6 Pounds


Alarm: ‎Smoke


Sensor Type: ‎Ionization


Number of Items: ‎2


Manufacturer: ‎Resideo


UPC: ‎029054022400


Part Number: ‎SMI100


Item Weight: ‎9.6 ounces


Product Dimensions: ‎5.6 x 5.6 x 1.9 inches


Item model number: ‎SMI100


Batteries: ‎1 9V batteries required. (included)


Size: ‎2-Pack


Pattern: ‎SMI100


Item Package Quantity: ‎1


Included Components: ‎9V Alkaline Battery


Batteries Included?: ‎Yes


Batteries Required?: ‎Yes


Battery Cell Type: ‎Zinc Carbon


Date First Available: September 21, 2023


Frequently asked questions

If you place your order now, the estimated arrival date for this product is: Sunday, Mar 22

Yes, absolutely! You may return this product for a full refund within 30 days of receiving it.

To initiate a return, please visit our Returns Center.

View our full returns policy here.

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Similar Products

Top Amazon Reviews

    • Replaced Exp First Alert Smoke Detectors w/New
Size: 2-Pack Style: Precision Detection Pattern Name: SMI100
Review Image by Newleaf Newleaf
Review Image by Newleaf Newleaf
Review Image by Newleaf Newleaf
Review Image by Newleaf Newleaf
I just installed these 2 First Alert smoke detectors, so I can’t give you a long time use review, but I’m happy with my purchase. These replaced two 10 year-old similar First Alert smoke detectors that had reached their expiration date. I was very pleased with those, which is why I looked for the same smoke detectors. I couldn’t find the exact same ones, so I replaced with these, which look similar and are basic like the first pair. Although the size of the new ones are a little bit smaller than the ones they replaced, I was pleased to find that the new brackets fit the 2 screws I already had in the walls from the old ones. I was concerned that I would be patching and drilling, but I didn’t have to, so installation was easy peezy. The other thing that is different on the new ones is that the batteries are 9 V versus the AAs for the old ones. I prefer AAs because it’s a battery that I always have around the house and they are easy to come by and inexpensive, relatively speaking. However, the new detectors came with batteries, so I don’t have to worry about replacing them for another year. ... show more
Reviewed in the United States on February 1, 2026 by Newleaf Newleaf
    • Smoke Detector
Size: 2-Pack Style: Precision Detection Pattern Name: SMI100
The First Alert SMI100 Battery-Operated Smoke Alarm (2-Pack) is a dependable and cost-effective solution for home fire safety. From installation to daily use, this smoke alarm performs exactly as expected and delivers reliable protection you can count on.
Reviewed in the United States on February 16, 2026 by jgloop
    • Good smoke detector
Size: 2-Pack Style: Precision Detection Pattern Name: SMI100
Easy to install. Works well. Loud alarm.
Reviewed in the United States on February 20, 2026 by Courtney T.
    • Update batteries to alkaline
Size: 1-Pack Style: Precision Detection Pattern Name: SMI100
Alarms arrived promptly and in good condition, packaged well. One caveat though, I highly recommend that you switch out the provided heavy duty 9 V batteries with your own fresh alkaline batteries. Reason being, one of the three detectors that I installed immediately started beeping a low battery warning, and upon testing the provided battery, it wasn't dead but it was very weak. The other two with the provided battery tested very strongly and were good batteries. Bottom line, pull the heavy duties, use them in something besides a smoke detector, and slap in some alkalines just to be safe. Great smoke detectors though, for sure. ... show more
Reviewed in the United States on November 7, 2025 by virginia sanford
    • Everyone should have
Size: 2-Pack Style: Precision Detection Pattern Name: SMI100
Works well. Had a little smoke while cooking and set off alarm.
Reviewed in the United States on December 19, 2025 by Walter c Elliott
    • Bang for the buck
Size: 2-Pack Style: Precision Detection Pattern Name: SMI100
Good band for your buck! Arrived in less time than estimated. Install is straight forward W/ nothing more than a Philips screw driver. At the cost point, these were the best value I could find. I would recommend them.
Reviewed in the United States on February 20, 2026 by Bingo Boy
    • Good product
Size: 2-Pack Style: Precision Detection Pattern Name: SMI100
Easy to install & works very well
Reviewed in the United States on February 10, 2026 by WIL
    • Functional standard size smoke alarm
Size: 1-Pack Style: Precision Detection Pattern Name: SMI100
Review Image by Suburban dwellers Suburban dwellers
It looks to be in perfect working order. It came with a plastic tab blocking the battery from discharging. You have to pull it out to get it to turn on. Not very hard to do, but someone with dexterity issues may need help pulling it out. It beeped when the battery was connected upon pulling out the tab. The test button seems to work. Haven't had any smoke yet to make it go off, so can't start to that yet. I was able to twist it into the mounted frame of the previous fire alarm. (Can't recall if it was the same brand) ... show more
Reviewed in the United States on January 11, 2026 by Suburban dwellers Suburban dwellers

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