How Long Do Carbon Monoxide Detectors Last?

It is 2 a.m. and your CO alarm starts chirping — one short beep every thirty seconds. You swap the battery, but the chirps come back within an hour. A quick look at the label on the back reveals a manufacture date from eight years ago. The alarm is not broken; it has reached its end-of-life. Most people do not realize that CO alarms are not permanent fixtures — the sensor inside ages and drifts, so every unit has a limited service life. This page explains why CO sensors expire, the typical lifespan ranges you will see in homes, what end-of-life signals look like, and how to pick a replacement cycle that is simple enough to actually maintain.

In 60 Seconds

• Most residential CO alarms last 5 to 10 years — the only correct number is the one on your specific unit's label.
• The test button checks electronics and sounder, not whether the sensing element is still accurate.
• End-of-life chirps continue even after a battery change — that means the entire unit needs replacing.
• Write the replacement date on the front of each alarm so you can check it without uninstalling.
• After installing a new unit, review placement and test monthly.

Quick Answer: Typical Lifespan Is 5–10 Years

Most residential CO alarms fall into a broad range of about 5 to 10 years. Many common models are closer to the 5–7 year range, while some sealed-battery designs and combination smoke/CO units are marketed with longer service intervals. The only "correct" number is the one on your specific alarm: look for a "Replace by" or "Do not use after" date on the label.

Why Carbon Monoxide Sensors Expire

A CO alarm relies on a sensor that reacts to carbon monoxide and converts that reaction into an electrical signal. Over years of normal exposure to humidity, temperature swings, household aerosols, dust, and low background contaminants, the sensor slowly drifts. Manufacturers build in calibration tolerances, but eventually the sensor changes enough that the device is no longer reliable.

That is why you can have an alarm that still powers on, still beeps during a test-button check, and still needs replacement: the test button mainly checks electronics and sounder, not whether the sensing element is "as good as new."

Lifespan by Alarm Type

Battery-powered CO alarms

Many battery-powered units have a service life in the mid-range (often around 5–7 years). They are easy to place and keep working during outages, but the sensor still expires on schedule. If your home relies heavily on battery units, your maintenance success depends on having a simple replacement plan.

Plug-in CO alarms (with or without battery backup)

Plug-in alarms are convenient, but they do not automatically last longer — lifespan is still driven by the sensor and the manufacturer's rating. The key difference is reliability during power outages: if it is plug-in only, it may go silent during an outage. A plug-in alarm with battery backup is usually a better choice.

Hardwired and combo smoke/CO alarms

Hardwired units are often installed in new builds or upgrades, and many are combination smoke/CO alarms. Service life can be similar to standalone CO alarms, but replacement can be more involved because you may be swapping multiple units at once. Use the date printed on each device and treat replacement as a batch job when possible.

"10-year sealed battery" vs "10-year sensor"

Some alarms have a sealed battery designed to last up to 10 years, which reduces nuisance low-battery chirps. That is a convenience win, but you still must follow the device's end-of-life or "Replace by" date. In many products those two dates align; in others, the battery life claim and the sensing life can differ.

How to Tell When Your CO Alarm Should Be Replaced

1. Look for a "Replace by" or "Do not use after" date on the back or side label.
2. If there is no explicit replacement date, find the manufacture date and check the manual for the service-life rule (for example, "replace 7 years after manufacture").
3. Check the display, if present: some models show a code when they reach end-of-life.
4. If you moved into a home with existing alarms, assume they may be old until you confirm dates.

Pro tip: write the replacement month and year on a small label on the front edge where you can see it without uninstalling the unit.

Common End-of-Life Signals

People often search for CO detector end of life because the beeps are confusing. End-of-life warnings usually have these traits:

• Regular chirps at a fixed interval (for example, every 30–60 seconds) that continue even after a battery change.
• Display messages such as "End", "EOL", or a specific error code.
• A reset that only works briefly, after which the chirp returns.

A true CO alarm event typically sounds louder and more urgent than a single chirp. If you are ever unsure, treat it seriously: get to fresh air and follow your alarm instructions. For troubleshooting chirps and patterns, see the dedicated guide on carbon monoxide detector beeping.

Replacement Checklist

After Replacement: Test and Document

Once you install a new unit, do three quick things:

1. Press the test button to confirm the sounder works.
2. Record the replacement date and location (a note in your phone is enough).
3. Set a reminder a month before expiration so you can replace proactively instead of during a 2 a.m. chirp.

If you are unsure how many alarms your home needs, use the how many carbon monoxide detectors do I need checklist to confirm coverage.

Sources & References

• CPSC: Carbon Monoxide Information Center
• NFPA: Carbon Monoxide Safety
• EPA: Where Should I Place a Carbon Monoxide Detector?

Published: January 15, 2024