A carbon monoxide detector lasts 5, 7, or 10 years depending on the model, and the printed label on the back of the unit is the only authority on when yours expires.
A CO alarm that still beeps during a test can still be a dead alarm. The sensor inside degrades quietly from the day it leaves the factory — it keeps powering on, keeps chirping, keeps looking fine, and stops reading gas accurately long before it ever tells you. That gap between “still runs” and “still protects” is where most homes get into trouble.
So the working rule is simple: replace the unit at the manufacturer’s stated end-of-life, not when the battery dies and not when the alarm starts acting strange. What follows is how to find that date, what the lifespan numbers actually mean, and the mistakes that quietly leave a home unprotected.
How Long Does a Carbon Monoxide Detector Actually Last?
Residential CO alarms are rated for 5, 7, or 10 years, and there is no single universal replacement age that covers every model sold in the U.S. The device’s own label and manual control.
Two current Kidde models show how the rating works in practice. In both cases the sensor is the component with the clock on it.
Battery Life vs. Sensor Life: The Difference That Catches People
A 10-year battery does not mean a 10-year detector, because the sensor usually expires first. The battery and the sensor are two separate clocks, and only one of them decides when the unit gets replaced.
On a sealed 10-year CO alarm, the design intent is that the sensor and the battery reach end-of-life together — the whole device is disposable, and you replace the unit rather than a battery. That’s the common configuration for modern lithium-powered models.
On older or plug-in units with replaceable batteries, the battery is a maintenance item and the sensor is the end-of-life item. Swapping in fresh batteries buys runtime, not protection. Once the sensor hits its rated ceiling, the alarm is done regardless of how new the battery is.
Where To Find Your Detector’s Replacement Date
The manufacture date is typically printed on the back or label of the alarm, and some guidance says to add the manufacturer’s stated lifespan to that date to get your replacement timing. That’s the date to trust.
- Pull the alarm off its bracket and turn it over. The manufacture date sits on the back label, often near the model and serial numbers.
- Find your model number in the same spot and check the manual or the maker’s website for that model’s rated life — 5, 7, or 10 years.
- Add the rated life to the manufacture date. A unit made in 2018 with a 7-year rating is due in 2025, no matter how well it still tests.
- Write the replacement month and year on the back with a marker, then set a phone reminder for 30 days before it.
If the label is worn or missing, treat the unit as expired and replace it. A CO alarm with no legible date gives you no way to know whether it’s still reading gas correctly, and there’s no safe way to guess.
When that date arrives, most households replace the whole unit — and a tested, current comparison of long-life models makes that choice faster. Our roundup of the best 10 year carbon monoxide detector options covers sealed units built to run their full rated span.
| Alarm Type | Rated Life | What Gets Replaced |
|---|---|---|
| Kidde alarms made before 2013 | 7 years | Entire unit |
| Kidde alarms made 2013 or later | 10 years | Entire unit |
| Kidde KN-COEG-3, KN-COPE-I, KN-COPP-3 | 10 years | Entire unit |
| Kidde K10LLCO (lithium battery) | 10-year sensor | Entire unit |
| Kidde K10LLDCO (digital display) | 10-year sensor | Entire unit |
| Plug-in units with replaceable batteries | Varies by model | Battery as needed, unit at sensor end-of-life |
| Unlabeled or illegible unit | Unknown | Entire unit, immediately |
The Mistakes That Leave Homes Unprotected
Four habits account for most of the risk, and each one involves trusting the wrong signal.
- Assuming every CO detector lasts 10 years. Plenty are rated for 5 or 7. The model number decides, not the category.
- Confusing battery life with sensor life. A fresh battery in an expired sensor is a working flashlight, not a gas alarm.
- Using the install date instead of the manufacture date. If the label specifies an end-of-life period from manufacture, the install date is irrelevant — a unit can sit in a warehouse before it reaches your wall.
- Keeping a unit past its stated end-of-life because it still powers on. Passing a test button press only proves the horn and circuit work. It says nothing about the sensor’s accuracy.
Manufacturer instructions are the controlling source here, and they override any general estimate — including the ones in this article. When the manual and a blog post disagree, the manual wins.
Kidde’s own carbon monoxide alarm replacement guidance spells out the seven-to-ten-year range and the model exceptions directly.
FAQs
Do all carbon monoxide alarms really last 10 years?
No. Residential CO alarms are rated for 5, 7, or 10 years depending on the model, and Kidde notes its pre-2013 units carried a seven-year life. The label or manual for your specific model gives the real number, and that’s the figure to use when scheduling replacement.
Can I just replace the battery and keep using my old detector?
Only until the sensor reaches its rated end-of-life. On sealed 10-year models the battery and sensor expire together, so the whole unit gets replaced. On units with replaceable batteries, fresh batteries buy runtime but do nothing for an expired sensor, which is what actually detects the gas.
Where is the manufacture date printed on a CO alarm?
It’s typically on the back or label of the device, often alongside the model and serial numbers. Some guidance says to add the manufacturer’s stated lifespan to that date to set your replacement timing. If the label is worn or unreadable, replace the alarm rather than guessing.
References & Sources
- Kidde. “When Should I Replace My Carbon Monoxide Alarm?” States the seven-to-ten-year replacement range and Kidde’s model-specific lifespan exceptions.
- Kidde. “Time to Replace Your Alarms?” Explains end-of-life replacement timing for smoke and carbon monoxide alarms.
- Sourcewell. “Smoke Alarm and Carbon Monoxide Testing and Replacement” Covers manufacture-date-based replacement timing for CO alarms.