CarbonOne Safe lifespan – how do I know when to replace it?

I just counted from the day I plugged mine in, that seemed like the easiest way. The self test beeps and checks the alarm part, but I don’t think it really tells you if the gas sensor itself is wearing out. I replaced mine around the 5 year mark anyway since the sensors don’t last forever.

Mine died at four years, no warning from the self test.

I had one of these in a rental a couple years back and the five-year thing bugged me too. The box said up to five years but there was nothing printed anywhere on the unit itself, which is annoying. My landlord had clearly just left it there from whoever lived there before, so I had no clue how old it actually was.

What I ended up doing was looking at the little screen one day and noticing the CO number wasn’t sitting at zero like it usually did. It was bouncing around 2 or 3 ppm in a room with no gas anything running. I opened a window, it went back down, so I figured it was just picking up something in the air. But then it kept doing it over the next few weeks even with nothing going on, and that made me start wondering if the sensor was just getting old and reading junk.

The self test never once flagged anything during that whole time. Beeped fine, lights did their thing. So from my experience the test is not catching a sensor that’s drifting. It just confirms the thing turns on and makes noise.

I ended up replacing it because I couldn’t verify the age and the readings looked off. If you know when you plugged yours in, counting from that date is probably the most honest number you’ve got.

I just use the date on my receipt since the box doesn’t have one. My last one lasted a little over four years before the numbers started acting weird, so I replaced it then.

Five years is not a hard deadline anyway. I replaced mine at five and a half because the readings still looked normal, and the new one behaved exactly the same. The self test is the only real gauge you have.

Self-test on mine never caught the sensor drifting, it only confirmed the alarm still sounds. I swapped it at the five year mark anyway. Figured a detector that misses gas quietly isn’t worth the gamble.

The self-test catching a dying sensor thing is where I’d push back. Everyone keeps saying it only checks the alarm, but that wasn’t my experience. Mine actually started false alarming on the gas side around year four, and when I ran the test it failed outright. So the test did catch something, just not in a way I expected. It wasn’t subtle drift either, it just went bad.

As for the date, I never counted from plugging it in. That seems off to me. The clock starts when the sensors are made, not when you finally get around to putting it in the outlet. Mine sat in a closet for maybe eight months before I used it, and I’m not pretending those months didn’t happen. I went off the sticker on the back.

What actually killed mine was the display. Numbers started jumping around for no reason, then it just showed dashes one morning. No warning from the self-test before that. So I replaced it and moved on. Roughly four and a half years of actual use, give or take.

If there’s genuinely no date anywhere on yours, that’s a problem with the packaging, not with you. I’d still count from the manufacture sticker if there is one, and from purchase if there isn’t. Counting from plug-in just buys you extra time you probably don’t have.

Just count from plugging it in, that’s what I did.

I’d count from the date it first went into the outlet, not when you bought it. That’s what I did with mine, and it’s the only date I can actually point to later. The box not having an expiry date is annoying though, especially since “up to 5 years” could mean anything from 3 to 5 depending on how it’s used. As for the self-test, I don’t think it tells you much about the sensor itself. Mine still beeped and showed all clear right up until I replaced it, so the test only proved the alarm part was working. If it’s already been running a few years and you’re second-guessing it, I’d rather swap it a bit early than keep waiting for a sign that might never come. The live display is nice to have, but it doesn’t really tell you if the sensing part is fading underneath.