Smoke alarms last 10 years from the manufacture date on the label, but carbon monoxide alarms range from 7 to 10 years depending on the model.
The age limit has nothing to do with whether the test button works — sensors degrade silently, and the date on the back is the only honest measure of whether it will respond to real smoke or CO.
Smoke and heat alarms: replace at 10 years. CO and combination alarms: 7 to 10 years depending on model. For current models and costs, see our guide to the best 10 year smoke and carbon monoxide detector.
Do Smoke Detectors And CO Alarms Have The Same Lifespan?
No — smoke alarms have a firm 10-year limit; CO alarms expire in 7 to 10 years depending on the model. Ionization and photoelectric smoke sensors hold up for a decade. Electrochemical CO sensors lose accuracy as they age, so some manufacturers cap them at 7 years. Kidde says combination smoke/CO alarms fall in that 7-to-10-year window based on the model — the box and manual will tell you.
The 10-year figure applies from the manufacture date, not the install date. A unit that sat in a warehouse two years before installation already has two years burned off.
Where Do You Find The Manufacture Date?
It’s printed on the label on the back of the alarm, usually as a date or date code. Fire officials urge residents to check this date and replace outdated units.
Ten years for smoke alarms; 7 to 10 for CO and combination units per your model. If it’s older than its rated life, replace it now, no matter how well it seems to work.
Constant high or low temperatures and high humidity quietly shorten that lifespan. A Kidde combination alarm product page notes both can reduce battery life, and the same stress wears on the sensor.
What Does The Chirp At End Of Life Mean?
On most modern alarms, that chirp is a replacement warning, not a battery warning — and it won’t stop when you swap the battery. Many sealed-battery units have no replaceable battery anyway.
Kidde’s guidance describes the end-of-life chirp as a signal the alarm has reached its limit. One Kidde guide notes ten-year CO alarms may chirp twice every 30 seconds to indicate end of life. Kidde’s official CO alarm replacement support page confirms a battery change is not the fix.
A single low-battery beep is a battery problem. Two chirps in a row on a repeating cycle means the alarm has expired.
Replacement Lifespan At A Glance
| Alarm Type | Rated Lifespan | Replace When |
|---|---|---|
| Smoke alarm | 10 years | 10 years from manufacture date |
| Heat alarm | 10 years | 10 years from manufacture date |
| CO alarm (post-2013) | 10 years | 10 years from manufacture date |
| CO alarm (pre-2013) | 7 years | 7 years from manufacture date |
| Combination smoke/CO | 7–10 years | Per model — check the manual |
| Sealed 10-year battery combo | 10 years | 10 years from manufacture date |
| Hardwired with battery backup | 10 years | 10 years from manufacture date |
A Few Traps That Trip People Up
- Kidde model exceptions. As of 2013, all Kidde CO alarms are 10-year units except the KN-COEG-3, KN-COPE-I, and KN-COPP-3. Pre-2013 CO alarms have a 7-year life. Treat those three models as 7-year units.
- Warranty is not lifespan. A “10-year limited warranty” covers defects, not a guarantee it works for a decade.
- It confirms the horn and circuit work, not that the sensor can still detect smoke or CO.
Current combination units like Kidde’s 30CUD10 and its 10-year battery-powered line advertise a full decade of sealed-battery operation — but the decade starts at the factory, not the install date.
FAQs
Do I replace a 10-year alarm at exactly 10 years, or wait until it chirps?
Replace it at 10 years from the manufacture date, even if it hasn’t chirped. The chirp is a backup warning, not the trigger for action.
Why do some CO alarms only last 7 years?
Electrochemical CO sensors drift and lose accuracy with age, and older designs were rated for 7 years. Kidde confirms all CO alarms made before 2013 have a 7-year life, and post-2013 models KN-COEG-3, KN-COPE-I, and KN-COPP-3 remain 7-year units.
Can I just change the battery to stop the end-of-life chirp?
No. The chirp signals the sensor has expired, not the battery. Sealed-battery alarms have no replaceable battery, and a new battery won’t stop an end-of-life warning on models that do. Replacement is the only fix.
References & Sources
- Kidde. “Carbon Monoxide Alarm Replacement.” Manufacturer guidance on CO alarm lifespan, the 7 vs. 10-year rule, and the end-of-life chirp.
- BRK Electronics. “How Long Do CO and CO/Smoke Combo Alarms Last?” Installer guidance on replacement intervals for combination smoke and CO alarms.
- WGBH News. “Check Your Smoke Detectors: Fire Officials Urge Mass. Residents to Replace Outdated Alarms.” Public safety reporting on the 10-year replacement rule and checking manufacture dates.
