First Alert SMI105-AC, Interconnect Hardwire Smoke Alarm with 10-Year Battery Backup, 1-Pack
Original price was: $39.99.$29.83Current price is: $29.83.
Price: $39.99 - $29.83
(as of Oct 09, 2025 14:13:49 UTC – Details)
The First Alert SMI105-AC Interconnect Hardwire Smoke Alarm with 10-Year Battery Backup uses First Alert’s Precision Detection advanced sensing technology and meets new industry standards. Interconnect multiple alarms together to help provide an early warning throughout your whole home and have peace of mind knowing the 10-year battery backup provides continuous protection in the event of a power outage.
First Alerts 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.
10-Year battery backup provides continuous protection during power outages
Through early warning interconnect, when one alarm sounds, all compatible
Alarm indicator visually identifies the unit that initiated the alarm
End-of-life warning lets you know when it’s time to replace the alarm
Customers say
Customers find the smoke detector easy to install and consider it a great replacement for older units, offering good value for money. The functionality receives mixed reviews, with some units working as advertised while others randomly false alarm. The battery life is also mixed, with some customers appreciating the 10-year backup while others report it doesn’t last. The chirping frequency and wiring receive mixed feedback, with some customers finding it loud and annoying, while others note the connecting wires are the same. The lifespan is mixed, with some customers reporting it lasts 5 to 10 years while others say it doesn’t last 10 years.
8 reviews for First Alert SMI105-AC, Interconnect Hardwire Smoke Alarm with 10-Year Battery Backup, 1-Pack
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Original price was: $39.99.$29.83Current price is: $29.83.
Anthony S –
Works Great â Once You Actually Install It (According to My Wife, 3 Months Late)
Bought this smoke detector because, you know, fire safety is importantâ¦Apparently not important enough for me to install it in under 90 days.But hey â I had other things to do. Like reorganize the garage. Twice.And stare at it in the box on the kitchen counter like it was going to mount itself.Meanwhile, my wife spent three months walking past it like she was in a house made of dry hay and open flames.Every time the oven turned on, I got the look.You know the one â the âIf the toaster sparks, weâre doneâ look.⸻ð¥ Smoke Detector FunctionalityOnce I finally summoned the courage (and a step stool), this thing installed easily and worked like a champ.Tested it with the âtoast testâ and yep â sheâs got lungs.Loud enough to wake the neighbors, the pets, and possibly the dead.I feel safer already. So does my marriage.⸻ðµ Value for MoneyExcellent. A small price to pay for not living in a potential fireball and regaining my wifeâs trust.Honestly, I shouldâve paid more just for the emotional damage I caused by procrastinating.⸻𧰠Quality & BuildSolid construction. Doesnât feel cheap or flimsy.You can tell itâs built to detect danger, not just hang out on the ceiling for decoration.⸻ð Ease of ReplacementSwapping it in for the old detector was fast and painless.If only me actually doing it had been that easy.Seriously, it took longer to unwrap it than to install it â once I finally picked up a screwdriver.⸻𧯠Final Thoughts:⢠Yes, it works great.⢠Yes, itâs loud, reliable, and makes us feel safe.⢠No, I canât explain why it took me a whole fiscal quarter to install it.Wifeâs happy. House didnât burn down.Marriage survived.10/10 would delay installation again (kidding, honey).
barbara hatfield –
GREAT & EASY TO REPLACE
EXACTLY WHAT I ORDERED WITH FAST SHIPPING & GOOD PRICE. I REPLACED MY GOING ON 10 YR OLD ONES HARD WIRED BUT THEY STILL HAD THE BATTERIES THAT HAD TO BE REPLACED EVERY YEAR OR SO.
farmboy –
Smoke detector upgrade
These were an upgrade to similar smoke detector from same manufacturer. They came as promised. Easy installation as they fit up to existing detector base and wiring connector. The operation indicator light is easier to see. Love the 10 battery idea. Matches the recommended replacment cycle of the smoke detectors. No more annual battery replacement!
Third Brain –
Installs Easily
Fit the previous model. The pin configuration on the images are correct. So far so good. Let’s see if this battery lasts and the sensor doesn’t go first. I’m using those cleaning covers when I vacuum now. I’m giving it 4 stars for the install and being what was listed. Can speak to how it lasts yet.
D. V. Guenther –
Quality
One day in and I love these smoke detectors. I didn’t need the CO detector combo because we have wall plug detectors already. I opted for the dumb model since I was going to add the SIGNIFICANTLY cheaper option of wiring a Zooz ZEN55 Z-wave relay to the detectors. This setup allows the detectors to become smart and alert me through my Home Assistant environment. Anyways, yeah, these 10-year battery models are great with a nice faint green glow indicating they are operational and in good condition.
Good book reader –
Well designed interconnected Smoke Alarm
I bought 7 First Alert SMI105 AC Smoke Alarms to replace existing units that were past their 10 year service life (Oops) and which required battery replacement every 5 years. I was delighted to learn that these new units used the same wiring and mounting brackets as the old 9120B model. So it was just a matter of unscrewing and disconnecting the old unit and plugging its old electrical connector into the new unit and then twisting the new unit into the old mounting bracket on the ceiling. Then all that was left to do was to pull out the plastic tab to activate the built in 10 year battery and test the unit. (Did you get that? No replacing batteries during the life of the alarm? WOW!) The only difficulty I had was in getting 7 units that were recently recently manufactured. What is got was a pkg of 3 made on 8/5/25, another pkg of 3 made in 7/29/24 and 1 made on 11/20/24 in spite of asking for 7 made on a recent date. Still working on that. So 5 stars for the smoke alarm design. Not so many for following delivery instructions though.
EasyReader –
I have confidence in these alarms
Very nice units. Fit easily on my old bases. Brand name which I trust. No annoying dead batteries!
Kelviemalia –
Chefâs worse critic
Works very well! Every time I try to sear a steak, this thing starts screaming like Gordon Ramsay in my kitchen. At least I know my house wonât burn down while I chase Michelin stars.