First Alert SMI105-AC, Interconnect Hardwire Smoke Alarm with 10-Year Battery Backup, 1-Pack
Original price was: $39.99.$29.80Current price is: $29.80.
Price: $39.99 - $29.80
(as of Nov 05, 2025 08:15:02 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 feedback, with some units randomly false alarming. The battery life and lifespan also get mixed reviews – while customers appreciate the 10-year backup battery, some report it doesn’t last, and while some units last 5 to 10 years, others don’t meet the 10-year claim. The wiring receives mixed feedback, with customers noting that the connecting wires are the same as expected.
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.$29.80Current price is: $29.80.
Anthony S –
Works Great — Once You Actually Install It (According to My Wife, 3 Months Late)
Bought this smoke detector because, you know, fire safety is important…Apparently not important enough for me to install it in under 90 days.But hey — 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 — the “If the toaster sparks, we’re done” look.⸻🔥 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 “toast test” and yep — she’s got lungs.Loud enough to wake the neighbors, the pets, and possibly the dead.I feel safer already. So does my marriage.⸻💵 Value for MoneyExcellent. A small price to pay for not living in a potential fireball and regaining my wife’s trust.Honestly, I should’ve paid more just for the emotional damage I caused by procrastinating.⸻🧰 Quality & BuildSolid construction. Doesn’t feel cheap or flimsy.You can tell it’s built to detect danger, not just hang out on the ceiling for decoration.⸻🔄 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 — once I finally picked up a screwdriver.⸻🧯 Final Thoughts:• Yes, it works great.• Yes, it’s loud, reliable, and makes us feel safe.• No, I can’t explain why it took me a whole fiscal quarter to install it.Wife’s happy. House didn’t 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.
gelli –
Easy to install
Purchased to replace malfunctioning alarm. Works fine.
Jaded –
so far, so good
I received what I ordered. These have built in batteries with 10 year lifespan, so there is no need to replace batteries every year. I ordered 7 of these and the battery lifespan started within a couple months of my purchase date – I didn’t receive anything old. The smoke alarms are all the same and easy to install. They have a third wire to use for networking.
Barkanyc –
Great Value for Great Technology
I have purchased many smoke alarms over many years, especially the earlier ones with batteries that went bad and needed to be replaced, always chirping in the middle of the night. I never considered buying the alarm with a 10 year battery life. So when the battery alerted me (probably the entire building) that I needed a new alarm I recalled that I could and should go with the 10 year upgrade which was very reasonably priced. Being a senior, partially disabled, and living in Manhattan, hardware and big discount stores are hard to find (especially at 2 AM!) so I remembered, Amazon Prime, next day. I am so grateful to have this option of convenience and availability. It has made life so much simpler.
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.
EON –
No more annual climbing of the ladder
Replacements for aged detectors, simply remove the old, connections matched and now I have a ten year battery. The price is reasonable, they are not attractive but seldom are smoke detectors.
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.