[Gina Vale]

It says up to 5 years but there’s no expiry date on the box. Do I just count from when I plugged it in? Also does the self-test actually catch a dying sensor or does it just test the alarm noise? Not trying to replace it too early but also don’t want to find out the hard way.

[Emma__L]

The date thing confuses me too, I just wrote the plug-in date on a piece of tape on the back of mine. The self test mainly checks the alarm and electronics as far as I know, not really whether the gas sensor itself has gone weak. So counting from first use is probably the safer bet.

[Maria_Bakes]

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.

[Carla D.]

The self-test doesn’t really tell you if the sensor is wearing out, in my experience. Mine kept passing every test right up until the CO readings started drifting weirdly low, and that’s when I swapped it. So I’d say pay more attention to the numbers on the screen than the beep test.

[Maya Foster]

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

[Ella Voss]

The self test is mostly a noise check, not a sensor check, so I wouldn’t trust it to tell you when it’s done. I write the date on mine with a sharpie, but I still swap it before five years.

[Linda Robinson]

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.

[Maya Chen]

I had one of these in my old apartment and honestly the five year thing was always kind of vague to me too. I didn’t really track it, just swapped it out when it started acting weird. The display on mine went a little glitchy near the end, showing weird numbers that didn’t match anything going on in the room. No alarm, no warning, just odd readings. That’s what made me finally replace it. So I’d say if the numbers start looking off, that’s probably your sign more than any date. Counting from plug in makes sense but if you moved it around or it sat in a drawer for a while that gets murky. I never put much faith in the self test either, it just beeps and that’s about it. Not really proof of anything.

[Cora Finch]

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.

[Alex Fisher]

Count from when you plugged it in, that’s what I do.

[Steve Rogers]

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.

[Zoe Matthews]

The date on the back of the unit is the thing to check. Mine had a small sticker with a manufacture date, not an expiry date, and that’s what I went off. Five years from that sticker, not from when I plugged it in. If yours doesn’t have one, then yeah, plug-in date is your best guess.

On the self-test question, I don’t think it tells you much about the sensor itself. It seems to just confirm the alarm and the electronics are working. So a passing test doesn’t really mean the gas sensing part is still accurate. I’m not sure there’s a way to know that without some kind of calibration, which these home units don’t offer.

I’m actually looking at replacing mine soon and trying to decide if it’s worth going with something that has a proper end-of-life signal. Curious if anyone has used one that does.

[Jason Brown]

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.

[Tom_Craig]

The “up to 5 years” thing is mostly marketing. Mine started throwing random low-level CO readings around year three, so I tossed it. A self-test only proves the buzzer works, not that the sensor still detects gas properly.

[Rachel Cole]

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.

[d4niel]

Mine has been plugged in for a bit over four years now and it’s still reading zero on a clean day, so I’m not rushing to swap it. But I did notice something the manual doesn’t really explain. The sensor inside these things has a limited amount of chemical it can react to over time. Once that’s used up it doesn’t fail loudly, it just gets less sensitive. So a unit that’s technically “on” can still be past its useful life.

The self-test on mine just runs through the alarm and the lights. It has never given me any hint about sensor health. That part bugs me a little since there’s no way to actually check the sensor itself.

My plan is to just replace it at five years regardless of what the display says. It’s a cheap thing to swap and I’d rather not gamble on a detector that quietly stopped doing its job.

[Riley1]

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

[MikeRobbins]

Count from the plug-in date, that’s the safest bet.

[Kelly Sun]

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.

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