Replace your carbon monoxide detector every 5 to 7 years, or sooner if the manufacturer specifies a different lifespan

Most carbon monoxide detectors have a built-in expiration date printed on the back or inside the battery compartment. Check yours now — if it was manufactured more than five to seven years ago, it needs to be replaced, even if it still beeps when you test it. The sensors inside degrade over time and stop detecting carbon monoxide reliably, which is why age matters more than whether the alarm still sounds.

Some detectors last only five years; others are rated for ten. The manufacturer's label tells you the exact lifespan. If you cannot find the date or the label is worn away, replace the detector. A detector with an unknown age is a detector that may not work when you need it.

Write the replacement date on your calendar or set a phone reminder for five years from now. This is the single most important maintenance task for carbon monoxide safety in your home.

Key Takeaways

  • Check the manufacture date on the back of your detector — if it is more than five to seven years old, replace it when ready.
  • The sensor inside degrades with age and stops detecting carbon monoxide reliably, even if the alarm still beeps during a test.
  • Some detectors are rated for five years, others for ten — the manufacturer's label on your unit tells you the exact lifespan.
  • Mark your calendar or phone for the replacement date so you do not forget when the detector expires.
  • A detector with no visible manufacture date should be replaced, because you cannot know how old the sensor is.

How to find the manufacture date on your detector

The manufacture date is usually printed on a label on the back of the unit or inside the battery compartment. It may say "MFG" or "Manufactured" followed by a month and year. Some brands use a code instead — for example, a series of numbers or letters that represent the production date. Check the instruction manual or the manufacturer's website if you cannot read the label clearly.

If the label has worn away or faded, you cannot reliably determine the age. Replace the detector rather than guess. The cost of a new detector is far lower than the risk of a failed sensor during a carbon monoxide leak.

Signs your detector may need replacement before the expiration date

If your detector does not beep when you press the test button, the battery may be dead — replace the battery first. If it still does not beep after a fresh battery, the sensor has failed and the unit must be replaced.

Some detectors have a "low battery" chirp that sounds every 30 to 60 seconds. This is normal and means the battery needs changing, not that the detector itself is broken. However, if the chirping continues after you install a new battery, the detector may be faulty and should be replaced.

If your detector is physically damaged — cracked casing, water damage, or corrosion — replace it. Damage can prevent the sensor from working correctly even if the test button still functions.

Where to buy a replacement detector

Carbon monoxide detectors are sold at hardware stores, home improvement retailers, and online marketplaces. Look for detectors that meet UL 2034 or IEC 60335-2-89 standards, which means they have been tested for accuracy. Most detectors cost between $20 and $60.

Battery-powered detectors are simpler to install than hardwired models and do not require an electrician. Plug-in detectors are also straightforward — you straightforward plug them into an outlet. If you have a hardwired detector connected to your home's electrical system, you may want to replace it with the same type, or hire an electrician to help you switch to a battery or plug-in model.

How to install your new detector

Place the new detector on a wall or shelf in a central location, away from windows, doors, and vents. Carbon monoxide rises and spreads throughout a room, so placement is less critical than with smoke detectors, but a central location helps the sensor detect gas quickly. Install at least one detector on each level of your home and one near any bedrooms.

If you are replacing a hardwired detector, turn off the power at the circuit breaker before removing the old unit. If you are unsure how to do this safely, contact a licensed electrician. For battery-powered or plug-in detectors, straightforward remove the old unit and install the new one according to the manufacturer's instructions.

Test the new detector by pressing the test button. It should beep loudly. If it does not, check that the battery is installed correctly and try again. Once you confirm it works, write the replacement date on the unit itself with a permanent marker.

Keeping track of replacement dates

The easiest way to remember when to replace your detector is to write the date directly on the unit with a permanent marker. Include the month and year you installed it, plus the month and year it will expire. For example: "Installed 3/2024 — Replace 3/2029."

You can also keep a home maintenance log in a notebook or digital file. List each detector's location, the date you installed it, and the date it expires. Review this log once a year, perhaps during spring cleaning or when you change your clocks for daylight saving time.

Set a phone reminder for one month before the expiration date. This gives you time to purchase a replacement and install it without rushing.

What to do with an old detector

Do not throw a carbon monoxide detector in the trash. Many contain radioactive materials or other components that require special handling. Check with your local waste management facility or hazardous waste collection program to find out where to dispose of old detectors in your area. Some retailers that sell detectors also accept old ones for recycling.

If you cannot find a local recycling program, contact the detector manufacturer — many have mail-back programs or can direct you to a disposal facility near you.

Frequently Asked Questions

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

Replace the battery if your detector is still within its lifespan and the test button works after you install a fresh battery. However, if the detector is five to seven years old or older, replace the entire unit. The sensor degrades with age regardless of battery condition.

What if I do not know when my detector was manufactured?

If you cannot find a manufacture date on the label or inside the battery compartment, replace the detector. You cannot know how old the sensor is, and an aging sensor may not detect carbon monoxide reliably. A new detector costs less than the risk.

Do I need to replace detectors in every room?

You should have at least one detector on each level of your home and one near bedrooms. Replace all of them on the same schedule if they were installed around the same time. If you installed them at different times, track each one separately and replace them as they reach their expiration dates.

What if my detector is hardwired to my home's electrical system?

Turn off power at the circuit breaker before removing a hardwired detector. If you are not comfortable working with electrical wiring, hire a licensed electrician to remove the old detector and install a new one. You can also replace a hardwired detector with a battery-powered or plug-in model if you prefer.

How often should I test my detector after I replace it?

Test your detector once a month by pressing the test button. It should beep loudly. If it does not beep, replace the battery. If it still does not beep after a fresh battery, the detector is faulty and needs to be replaced.