First Alert SMI100-AC, Hardwire Interconnect Smoke Alarm with Battery Backup, 1-Pack
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Availability:
In Stock.
Arrives
Tuesday, Apr 28
Size: 1-Pack
Style: Precision Detection
Pattern Name: SMI100-AC
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.
- 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
Description
The First Alert SMI100-AC Hardwire Interconnect Smoke Alarm with Battery Backup meets new industry standards utilizing First Alert's Precision Detection advance sensing technology. This hardwire smoke alarm is easy to install and replace existing alarms with no need to rewire. Plus interconnect compatible alarms to create a whole home alarm system to help provide an early warning.
Brand: First Alert
Style: Precision Detection
Power Source: Corded Electric
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
Global Trade Identification Number:
Number of Items: 1
Power Source: Corded Electric
Alarm: Smoke Alarm
Sensor Type: Ionization
Product Style: Precision Detection
Color: White
Item Dimensions D x W x H: 5.6"D x 5.6"W x 1"H
Item Weight: 0.6 Pounds
Brand: First Alert
Model Number: SMI100-AC
Global Trade Identification Number:
Manufacturer: Resideo
UPC: 029054022462
Item Type Name: Smoke Alarm
Built-In Media: Easy Adapter Plug, 9V Alkaline Battery
Unit Count: 1.0 Count
Frequently asked questions
If you place your order now, the estimated arrival date for this product is:
Tuesday, Apr 28
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.
To initiate a return, please visit our Returns Center.
View our full returns policy here.
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Similar Products
Top Amazon Reviews
Size: 1-Pack
Style: Precision Detection
Pattern Name: SMI100-AC
I got this as a replacement for an older hardwired smoke alarm, and it was pretty straightforward to swap in. The included quick connect plug made the setup easier, and it fit nicely once mounted. I also like that it has battery backup, so it still gives some peace of mind during a power outage. One thing I appreciated is that it is made to reduce nuisance alarms from normal cooking smoke, which is honestly a big deal if your old detector was too sensitive. The test/silence button is easy to reach, and the alarm feels solid, not flimsy or cheap. It also has the interconnect feature, so compatible alarms in the house can sound together. This is not a fancy smart unit, but for a dependable hardwired smoke alarm, it does the job well. Price felt fair, install was easy, and overall it seems like a solid upgrade from older builder-grade detectors.
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Reviewed in the United States on April 2, 2026 by Yifan jin
Size: 1-Pack
Style: Precision Detection
Pattern Name: SMI100-AC
This smoke alarm gives great peace of mind and works exactly as expected. Hardwired with backup Continuous power with battery backup for safety. Interconnect feature All alarms sound together, which is a huge plus. Easy installation Straightforward setup and fits standard wiring. Dependable brand First Alert is known for quality and reliability. Bottom line: A dependable, no hassle smoke alarm that’s perfect for home safety. Highly recommend.
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Reviewed in the United States on March 22, 2026 by Alter
Size: 3-Pack
Style: Precision Detection
Pattern Name: SMI100-AC
Upgrading our home’s smoke alarms to this 3-pack was a smooth and worthwhile improvement. From start to finish, the process was much easier than I expected. Installation was straightforward, especially if you’re replacing existing hardwired units. The wiring harness connected cleanly, and the mounting brackets lined up without any hassle. Once installed, setup was quick—everything synced as expected with the interconnect feature, so when one alarm is triggered, they all sound. That added level of coverage brings real peace of mind. The battery backup is another big plus. It’s reassuring to know the alarms will still function during a power outage without needing to think about it. The access for the battery compartment is simple and user-friendly, which makes future maintenance easier. I also appreciate the clean, low-profile design. It blends into the ceiling without drawing attention, but still feels solid and well-built. The test/reset button is easy to access, and the alarm itself is loud and clear—exactly what you want in an emergency. Overall, this set delivers on reliability, ease of installation, and essential safety features. If you’re looking to replace older hardwired alarms or upgrade to a system with interconnect capability, this is a practical and dependable choice that doesn’t overcomplicate the process.
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Reviewed in the United States on March 25, 2026 by Hannah
Size: 6-Pack
Style: Precision Detection
Pattern Name: SMI100-AC
Bought 9x detectors to replace existing ones that were well past there sell buy date these were the direct replacements for the original ones, both packages 6x & 3x arrived on time and no damage ( bought from different suppliers), installation was very easy I did not have to use the new connectors leads that were supplied as the originals were the same, one tip mark the body and mounting bracket with a pencil at the locked in position and removal points for installation it makes it a lot easier and also the battery door lines up ok, when you next need to replace the battery, all alarms connected and tested ok, finally READ the instructions there is a lot of info re: alarms and trip indications with the state of the power green led and the red alarm activated led, good value on Amazon.
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Reviewed in the United States on March 9, 2026 by Steve S
Size: 1-Pack
Style: Precision Detection
Pattern Name: SMI100-AC
It was time to replace my hardwired smoke detectors and while there are tons of brands with fancy features, I want reliability and a proven track record. I am not risking my family's safety on some discount smoke detector so I went with First Alert. I had Kidde smoke detectors previously so I had to replace the base and rewire them but it is a simple process that takes about 10 minutes for each detector from start to finish. They have only been installed a few days but they seem to work well. They include 9v batteries but be sure to check them as well as the date stamped on the back of the detector to make sure you are getting new products. My only complaint about the smoke detector design is the pivoting tray used to hold the battery - 2 of 4 were very difficult to close and the plastic is very rigid and felt like it would snap. The marks for positive/negative can also be a bit hard to see. It is worth mentioning that the green power light is very bright. It doesn't bother me but could be an issue for some. I recommend these detectors though I had a lot of issues ordering from Amazon. They do not sell 4 packs so I ordered a 3 pack and a single detector. I purposely ordered products that were shipped by Amazon but that is not what happened. The single detector was sent immediately from a 3rd party...not Amazon but whatever. It was 2 months old and seemed fine. I was informed the 3 pack of detectors was being sent by some other 3rd party and was delayed a couple of days. So Amazon just decided to use a 3rd party even though I actually paid more to get it shipped by Amazon. Then the delay was a week and it still didn't arrive and tracking showed it hadn't even been shipped. I cancelled the order and placed another making certain it was to be shipped from Amazon. Except it wasn't. Instead, it was shipped by another 3rd party and was delayed again, this time with no definitive delivery date. I had to cancel that order and went to Lowes where I paid more but at least I had them. Thankfully the single detector that was sent initially worked fine. I recommend the smoke detectors but I did not have a good experience ordering through Amazon.
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Reviewed in the United States on August 26, 2025 by MurphysLaw
Size: 3-Pack
Style: Precision Detection
Pattern Name: SMI100-AC
The price is right. Had wire with it easy install
Reviewed in the United States on April 11, 2026 by Jan
Size: 1-Pack
Style: Precision Detection
Pattern Name: SMI100-AC
Super easy to install and perfect match for the old detector that hit its 25 year life. Loosen screws and slip off the old hub and install new hub connect existing wire plug and bingo done in 5 minutes. Hope the new replacement lasts as long.
Reviewed in the United States on March 17, 2026 by Narelle Bedford