First AlertSCO501CN-3ST Wireless Interconnected Combination Smoke and Carbon Monoxide Alarm with Voice Location, Battery Operated (pack of 1)

Update: A little cooking accident caused a lot of smoke (no fire). The nearest alarm went off properly, and all of the linked alarms went off as well. Silencing the alarm required holding down the silence button for five seconds or so, which silenced all of the linked alarms.This review is based ONLY on the installation and setup.I just installed 7 units. The installation is very easy...took me about 60 seconds per unit to install the mounting rings.. You'll need a Phillips head screwdriver and a drill with a 3/16 bit for the mounting holes. I'm pretty handy with tools, but there was nothing involved in this that a novice should have difficulty with.Follow the instructions for where they should be mounted. There is a "dead zone" where walls and ceilings meet. Smoke detectors are ineffective in that zone. The previous owner of my home mounted all of the old detectors right in the dead zone. Oops.The programming is easy IF you read the directions and follow them exactly. Women should do fine; men will probably have to try programming a couple times before they figure out which simple step they overlooked. (I got it on the second attempt.) If you are overdue for new bifocals like I am, you might need a magnifying glass.The programming took less than a minute per unit when I did it correctly.Use hearing protection while you are programming and and testing. Seriously. All of the units will be going off at the same time on the table in front of you. At 85 decibels each, it is extremely loud,My total project time for installing all 7 was about 45 minutes hour from opening the box to putting up my tools.My units are spread out over three levels of the house (one in the basement, two on the first floor, one in an upstairs hallway, and one in each of three bedrooms). No issues with them communicating with each other. I tested each one individually and made certain it was communicating with all the others just to be sure. Running up and down all the stairs 7 times was a good workout. Again, hearing protection is advised. I have no doubt we will all be awakened if we ever have a fire in middle of the night.I really like the voice feature. If I have an alarm I will not have to go running through the house to figure out where the problem is. It clearly enunciates which unit is going off.Hopefully I will never find out how they operate in an emergency. I will update if I have any operational issues.

Our last house had hard-wired alarms which we had installed as part of a big remodel we did 20 yrs ago, 1 in each of 4 bedrooms, the hallway, the family room, the living room, and 2 in a very large home office/studio/work area. When we moved into our current place it had only 3 battery-powered alarms, 1 on each level, and I wanted the same reliability of connected alarms, but the cost of re-wiring was more than we could afford. I did some research and was hesitant about wirelessly-connected alarms at first, because the reviews didn't strike me as enthusiastic or that the alarms were reliable to the point of staking one's life on them.As time wore on my anxiety about having just the minimum number of alarms just nagged at me. I took a little gamble and ordered some of these. They were easy to install and easy to program. The also have a feature that lets you choose from a list of locations (that are common to most homes) to be spoken as part of the alarm, so you know the location/room of which alarm triggered the announcement. That's something even our hard-wired units didn't do.They use 2 AA batteries each, which are easy to replace simply be twisting/'unscrewing' the alarm unit from its' mounting plate. No screws must be unscrewed to replace the batteries, but they DO have a locking feature that is a plastic "pin" that comes as part of the unit and can make it difficult to open the battery compartment. You do NOT need to use it for the alarm to function, but it seems like something useful to landlords if renting out space. I did not use the pin to lock the battery compartment, as we're empty nesters and my spouse won't use a step stool yet alone a ladder. All mine are mounted on ceilings, so I need a step-stool/ladder to reach them, but they remove very easily. It's VERY unlikely anyone in our household is going to fiddle with the batteries.Know that the programming is a 2-step process when you are connecting more than 1 to the alarm "loop". The instructions were pretty easy to follow, and after connecting 2 or 3 units, you'll likely be able to do it without referencing them. NOTE THAT THE PROGRAMMING INSTRUCTIONS ARE ON A SEPARATE PAPER FROM THE INSTALLATION INSTRUCTIONS. The documentation states that each alarm unit should be within 100 feet of the next nearest unit, likely more than adequate for most homes.I installed 4 in August of '23, and now, more than 8 months later, have had no false alarms yet. I like them so much I ordered more for additional locations throughout the house. (I'm a heavy sleeper and also am hearing impaired and wanted to increase the likelihood of hearing any alarm).Note, too that YOU DO NOT NEED TO PROGRAM THEM FOR CONNECTIVITY, but if you don't, you might do better buying single units without the communication feature.Pricier than "single" units, yes, but if you want the extra protection of connected units and you need/want combination Smoke/CO2 alarms and can't/don't want to spend the money for hard-wired units, , I'd recommend these.

So I spent way too many hours trying to figure out what happened. We have several SCO501CN in our home that failed after several years and they worked so well, I wanted to replace each one of them. What we liked was: no false alarms, voice instead of crazy beeps when there is a problem, and interconnected. I ordered five from Amazon (Amazon.com as the seller) and was surprised to get an entirely different model. What was sent was the SCO500 which hardly appears anywhere on the internet. I did find it on First Alert's website however it wasn't clear that it was a voice model, which is what we really liked about the SCO501CN. The packaging also says nothing about voice. There is even a sticker with a bar code that says SCO 501CN on some of them, right below where the packaging clearly indicates that this is the SCO500...so weird. However, I opened one up and low and behold, it was voice, and CO, and smoke and interconnected, exactly what we wanted. It appears that the US has updated their requirements (UL STD 217) for smoke detectors due to the increasing number of lithium battery caused fires, and these models are consistent with this standard.So hopefully the new SCO500 works as well as the SCO501CN and thus far after a few weeks, no false alarms and they all installed easily (and into the same ceiling base as the old ones). Hopefully Amazon will update the listing for this at some point. I was told in November by their customer service that they would however still nothing yet.