First Alert SMICO105-AC, Interconnect Hardwire Combination Smoke & Carbon Monoxide Alarm with 10-Year Battery Backup, 3-Pack

Replaced my old ones with these 10 year battery units. They were an exact replacement and they all tested good. Very easy to replace.

Exactly what I needed and it was easy to install. It worked on the self-test and now I don’t need to worry about the battery for 10 years. The plug fit the wire from my ceiling perfectly with no adapter or rewire needed. The 10 year old plastic ring base didn’t fit the new alarm, but it was very easy to replace that using the existing screws and electrical box that was already there in my ceiling. I didn’t even need to remove the screws, just loosen them to twist off the old and replace it with the new then tighten the screws. It only took a minute or two.

Recently, the carbon monoxide/smoke detectors I had installed in my home soon after we moved in started making strange beeps. They weren't triggered and the batteries weren't dead. Turns out they EXPIRE after ten years, thanks to natural sensor degradation. Nothing can be done for this, and they won't stay quiet for long--my only choice was to remove them and get new ones. Older ones don't have this feature--they just hang out like they're protecting you, but DON'T, so expiring is actually a good thing. Since they only last 10 years, these have the additional option of including a sealed, non-replaceable battery that's guaranteed to last the entire 10 years! No more battery changes, just a new unit every 10 years. They're easy to install, and if your system is wired into your house so that all of them trigger when one does, it's a simple plug-and-play if your prior system had the same connectors. If not, you can replace them yourself if you're qualified, or have them installed for you, available through Amazon. These were no trouble at all to install and now there's no more need yearly battery swaps, a win in my book.

The smoke detectors in our house all needed to be replaced. They were around 10 years old and one of them started the chirping pattern indicating it was malfunctioning. Our prior smoke detectors were hardwired and were made by First Alert. These looked like a great replacement option, especially since they do not require 9 volt batteries; that's right, these have a 10-year battery pre-installed so you'll never get that 3:00am battery chirp. Installation was fairly simple since the wiring harness from my old First Alert smoke detectors was nearly identical to these. I had to replace the mount, but the old wiring harness just plugged into the new smoke/CO2 detectors. A couple things to note here. First, the mounting rings from the old detectors were not compatible with the new ones. Not a big deal to loosen a couple screws and swap the mounts. Second, the mounting rings on my new smoke/CO2 detectors are about a half inch smaller than my old smoke detectors. Also not a big deal, but I can see a paint ring around a couple of my detectors where we repainted the ceiling with the old detectors in place. You can see the size difference in the photo with my old smoke detector on the left (with an X on it) and my new one on the right. It took me less than 3 minutes to replace each detector. A couple suggestions for installation: 1. Write the installation month and year in bold pen on the outside of your new smoke/CO2 detector. 2. Make sure you can read the installation date from the main part of the room you install it in. That way you can easily see when the unit needs to be replaced. 3. Pull the battery tab before climbing a ladder (if you need a ladder). The clear plastic tab can be difficult to remove and you don't want to fall off your ladder. 4. Make sure you test every smoke/CO2 detector after you install it. Listen carefully to make sure the interconnect feature works (this is where triggering one detector makes them all go off). I had one defective detector in the bunch that triggered the one in front of me, but did not trigger any of the interconnected ones. These were reasonably priced for what you get. It's a smoke detector and a CO2 detector (though you should also have a CO2 detector closer to your floor as CO2 is heavier than air). They were simple to install, and I won't have to mess with any 9 volt batteries. So why 4 stars? I had one defective detector out of nine. The interconnect feature didn't work on it, and I almost missed that it had issues because the one I was testing still made noise. Would I buy them again? Yes, they are still a good value, look fine, and don't require any additional batteries.

I have always liked First Alert products, so it is no surprise I bought this later model. These units are totally compatible with my earlier 9120B units, so you could make installation very, very easy and retain the older ceiling mounting collars, and simply plug in the new units and screw to the existing collar. However, all plastic tends to yellow over the years, so for appearance I replaced the mounting collar as well. The collars are compatible with the older ones, so I could use the existing screws. No need to unscrew completely, as they have keyhole slots. Twist to release the old collar, twist to tighten the new collar, insert the plug and twist to tighten the new unit. I am pleased that these have carbon monoxide detection - very dangerous because you cannot see the gas. Awesome that they have 10 year rechargeable battery!!! No more "chirping" at 2 am!!!!

having both CO2 and smoke detection could be a life saver. Easy to install and great instructions

Purchased a three-pack and a one-pack SMICO105-AC to replace my 4 smoke alarms with smoke and CO alarms. The plug was incompatible with my 2004 units (OMG, I should have replaced these 10 years ago!) so I had to redo from the wire nuts. I fumbled a bit on the first two, but had it down by the last two. All seem to be working just fine. Found that it was rather hard to twist the unit on/off from the ring on two of them. Seems the circular paper insert on the unit was obstructing a bit. Also had my neutral wire come off once when stuffing wires back into box. Had a continuous three beep alarm that only went away when flipped the breaker to off. Was not in the manual. But I knew something was wrong and checked the wire nuts and quickly determined my error. Recommend that you use a pair of non-marring pliers (like needle nose) to hold wires firmly while you twist the wire nut on with force. Base ring fit the screws on my standard boxes just fine.

Like others have said, super easy to replace.