Replace your carbon monoxide detector every 5 to 7 years, or sooner if it fails a test or stops responding

Most carbon monoxide detectors have a lifespan of 5 to 7 years. After that, the sensor degrades and may not catch dangerous levels of carbon monoxide in your home. Check the back or bottom of your unit for the manufacture date — it is usually printed as a four-digit code where the first two digits are the month and the last two are the year. If that date is more than 7 years old, replace the detector now, even if it still beeps when you test it.

Some detectors have an end-of-life warning: a chirp or beep that sounds different from the low-battery alert, often accompanied by a light on the unit. If your detector makes this sound, the sensor has reached the end of its useful life and needs to be replaced when ready. Do not ignore this signal — it means the detector can no longer be trusted to warn you of a real emergency.

Key Takeaways

  • Carbon monoxide detectors lose sensitivity after 5 to 7 years and should be replaced on that schedule, regardless of whether they still seem to work.
  • Check the manufacture date on the back of your detector; if it is older than 7 years, buy a replacement now.
  • An end-of-life warning — a different-sounding chirp or beep — means the sensor has failed and the detector must be replaced when ready.
  • Test your detector monthly by pressing the test button; if it does not beep, replace it even if the manufacture date has not reached 7 years.
  • Keep a record of when you installed each detector so you know when the 5- to 7-year window closes.

Signs your detector has failed before its time

A detector can fail early if it has been exposed to extreme heat, humidity, or physical damage. If you press the test button and nothing happens — no beep, no light — the detector is dead and needs to be replaced when ready. This is the most reliable sign that the unit is no longer working.

Repeated low-battery chirps that continue even after you replace the battery also signal a failing detector. The battery is fine; the unit itself is not responding correctly. Replace the detector rather than troubleshooting further. Similarly, if the detector has been exposed to a fire, flood, or chemical spill in your home, replace it even if it still beeps — the sensor may have been compromised.

How to track replacement dates

Write the installation date directly on the detector with a permanent marker, or keep a list on your phone or in a household maintenance file. Many people forget when they installed their detectors, which is why the manufacture date on the back is your backup reference. If you cannot find the manufacture date and do not remember when you installed it, assume it is older than 5 years and replace it.

If you rent, ask your landlord or property manager when the detectors were last replaced. In most jurisdictions, landlords are required to maintain working detectors, so they should have this information. If they do not know or cannot provide proof of recent replacement, request new detectors in writing and keep a copy of your request.

What to do when you replace a detector

Turn off the power to the hardwired detector at your circuit breaker before removing it. If it is battery-powered, straightforward remove the old unit and install the new one in the same location. Most detectors mount on a wall or ceiling with screws or adhesive strips — use the same mounting method as the original unless the new unit comes with different hardware.

After installation, press the test button to confirm the new detector works. Write the installation date on the new unit. If you have multiple detectors in your home, stagger their replacement dates so you are not replacing all of them at once — for example, replace one every other year rather than all five in the same month.

Where detectors wear out fastest

Detectors in kitchens, garages, and bathrooms tend to fail sooner because they are exposed to steam, dust, and temperature swings. If your detector is in one of these locations, check the manufacture date every year and consider replacing it at the 5-year mark rather than waiting until year 7. Detectors in stable, climate-controlled bedrooms and living rooms typically last closer to the full 7 years.

Detectors mounted near furnaces, water heaters, or stoves also experience more wear. The heat and vibration from these appliances can degrade the sensor faster than normal. If you have a detector in a high-stress location, treat it as a higher-priority replacement item.

Choosing a replacement detector

When you buy a new detector, look for one that meets UL 2034 standards — this is the safety certification that confirms it will detect carbon monoxide at the levels required by law. Most detectors sold in hardware stores carry this certification. Battery-powered detectors are simpler to install if you do not have hardwired units, but hardwired detectors with battery backup are more reliable because they do not depend on you remembering to change batteries.

Some newer detectors include digital displays that show the current carbon monoxide level in your home, which can be useful for tracking whether appliances are leaking small amounts of gas. These cost more but give you more information. For basic protection, a standard UL 2034–certified detector is sufficient.

Frequently Asked Questions

Can I just replace the battery instead of the whole detector?

No. The battery powers the detector, but the sensor itself degrades over time. Replacing the battery will make the low-battery chirp stop, but it will not restore the sensor's ability to detect carbon monoxide. After 5 to 7 years, the entire unit must be replaced.

What if my detector is hardwired and I am not comfortable removing it?

Turn off the breaker that controls the detector, then unscrew it from the ceiling or wall. The wiring is usually a straightforward plug-and-socket connection that you can disconnect by hand. If the wires are soldered or spliced, call an electrician — they can replace it safely for a reasonable fee.

Do I need to replace all my detectors at the same time?

No. Replace each detector based on its own manufacture date. If you have five detectors installed in different years, you will replace them in different years. Staggering replacements spreads the cost and ensures you always have working detectors in your home.

What should I do with the old detector?

Most detectors contain small amounts of radioactive material in the sensor, so they should not go in the trash. Check your local waste management website for hazardous waste collection days, or ask your hardware store whether they accept old detectors for recycling.

Will a detector that is past its expiration date still beep if there is carbon monoxide?

It might beep, but you cannot trust it. The sensor degrades gradually, so an old detector may miss dangerous levels of carbon monoxide or respond too slowly. This is why age-based replacement is important — you need a detector you can rely on, not one that might work.