Review on FIRST ALERT BRK CO5120BN: Reliable Hardwired Carbon Monoxide (CO) Detector with Battery Backup in White by Nick Ward

I brought three CO5120BN carbon monoxide detectors to replace three that a contractor installed six years ago. One of the original units started beeping (5 beeps) every few minutes. The original block lasted six years before coming to an end. I don't think it's that bad. Having replaced all three of my original devices, even though only one reached the end of its lifespan, I am confident that I have at least 5 more years of protection. The swap was easy and only took a minute per device. Before proceeding with the installation, do a little trick: take a sharp blade and cut off the outer edge of the foam backing. For some reason the foam pad is slightly larger than the block itself.