Recently, the Firex smoke and carbon dioxide alarm on the first floor of my home started beeping. It was an unusual double-beep, not the usual low battery sound I’ve heard it make before. (Also unusual is that the beeping started during the day, not in the wee hours of the morning, as is usually the case. Just happenstance, I’m confident, but a welcome change.)

After much searching and reading online, I learned that a Firex double-beep signals that the detector has stopped working and needs to be replaced.

Unfortunately, Firex was absorbed by Kidde a few years ago. (The date of manufacture on my detector was 2004, so it should have been replaced years ago, but seriously, who checks their smoke detectors for an expiration date?)

Thankfully, the Kidde i12010SCO is a replacement for the hard-wired Firex FADC that I had. It just needs a plug adapter to connect to the Firex wires. (The wires power the device, even though it has a battery, and they signal other detectors in the home to sound off when any of the detectors are triggered.)

I opted for this particular Kidde because it has a built-in 10-year Lithium battery, which by the time the battery dies, the detector will have reached its expiration date.

I should mention that even with the necessary wiring adapter, there’s a tiny bit of work involved. The mounting ring that held the Firex needs to be replaced with the one for the Kidde, but in my case, that was just a couple of screws.