Maintenance procedure · Written to ASD-STE100 Issue 9 · Formatted to ANSI Z535

Carbon Monoxide Alarm Age Check and Replacement

Household CO alarms — the date of manufacture, the end-of-life signal, and replacing the unit
ApplicabilityHousehold carbon monoxide alarms, including plug-in, battery and combination smoke and CO units, within reach from the floor or from a stable step stool
Task time17 min to 27 min editorial estimate, not a measurement
PersonnelOne
Revisionv1 · 2026-07-29
BEFORE YOU BEGIN

Before you begin. This procedure is general reference information, not professional advice. Equipment varies by manufacturer, model, and year. Always follow the documentation supplied with your equipment — where it differs from this page, follow the manufacturer. Verify that you have the tools, the working conditions, and the ability to do this task safely. If anything is unclear, if the equipment is damaged, or if the task exceeds your experience, stop and use a qualified professional. You are responsible for your own safety and for the outcome. This site accepts no liability for any loss, damage, or injury arising from the use of this information.

Specifications marked unverified could not be traced to a manufacturer source. Do not rely on them — obtain the value from your equipment documentation.

Summary

A carbon monoxide alarm has a sensor with a finite working life, and it can reach the end of that life while still looking perfectly healthy on the wall. This page covers three things: the date of manufacture on the back label, the end-of-life signal that a fresh battery will not silence, and swapping the unit out. It is not about what to do when the alarm is actually going off. If your CO alarm is sounding right now, stop reading and get everyone outside into fresh air, then call 911 from outside. CPSC is explicit that you do not go looking for the source and you do not go back in until the responders say you can.

How long a CO alarm lasts is genuinely disputed, and this page publishes the disagreement instead of picking a winner. CDC says to follow the manufacturer's instructions or replace the detector every five years. Kidde, one of the largest manufacturers, says its own alarms have a proven life of seven to ten years depending on the model, that everything it built from 2013 onwards is a ten-year unit, and that anything older than that is a seven-year unit. CPSC publishes no universal number at all and says the recommended replacement age comes from the product literature or from the manufacturer. Those cannot be averaged into a fourth answer that belongs to nobody. The number that governs your alarm is the one printed on your alarm and in its manual, so this page shows you how to go and find it.

Safety

WARNING

IF THE ALARM GIVES A CONTINUOUS SIGNAL, MOVE ALL PERSONS OUTSIDE IMMEDIATELY.
Then call 911 from outside. Do not look for the source. Carbon monoxide can kill you before you feel the symptoms.

Necessary equipment

ItemNote
Flashlight optionalThe label on the back of the alarm is small.
Pen and paperUse these to record the date of manufacture.
Documentation for the alarmThe documentation gives the replacement age and the meaning of each signal.
New carbon monoxide alarm materialOnly necessary if the alarm is at the end of its life.

Before you start

Estimated 1 min

NOTEA continuous loud signal is an alarm condition. A short signal at regular intervals is a maintenance signal. Do not confuse the two.
  1. Listen to the alarm before you touch it.
    <1m
  2. If the alarm gives a continuous signal, move all persons outside to fresh air.
    • Do not look for the source of the carbon monoxide.
    • Call 911 from outside the home.
    • Count the persons outside.
    • Do not go into the home again until the responders permit it.
    <1m
  3. If the alarm gives a short signal at regular intervals, continue with this procedure.
    <1m

Find the age of the alarm

Estimated 5 min to 10 min

Alarm replacement age
Unverified — do not rely on this value
CONSULT THE DOCUMENTATION FOR YOUR ALARM

No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.

The sources disagree and this page does not reconcile them. CDC (cdc-carbon-monoxide-basics) says to replace a CO detector following the manufacturer's instructions or every 5 years. Kidde (kidde-co-alarm-replacement), a manufacturer, states a proven life of seven to ten years for its own alarms: a 10-year life for everything it built from 2013, and a seven-year life for anything it built before then. CPSC (cpsc-carbon-monoxide-fact-sheet) publishes no universal figure at all and says the recommended replacement age comes from the product literature or from the manufacturer. All three were accessed on 2026-07-29. Read the figure for your own model and use that one.
WARNING

DO NOT REMOVE THE MOUNTING PLATE OF AN ALARM THAT HAS WIRES.
The wires behind the plate can give you an electric shock.

  1. Remove the alarm from the mounting plate or from the electrical outlet.
    • Turn an alarm on a ceiling counterclockwise to release it.
    • If the alarm has wires, do not disconnect the connector.
    • Hold the alarm with one hand.
    <1m
  2. Read the date of manufacture from the label on the back of the alarm.
    • The date format is different for each manufacturer.
    • A flashlight makes the small print legible.
    1m
  3. Write the date of manufacture in your records.
    <1m
WARNING

INSTALL THE ALARM AGAIN IMMEDIATELY AFTER YOU READ THE LABEL.
The home has no protection from carbon monoxide while the alarm is off the wall.

  1. Read the replacement age from the documentation for your alarm.
    • The replacement age is different for each model.
    • The documentation of the manufacturer is the only correct source of this value.
    • Install the alarm again while you look for the documentation.
    2m
  2. If the alarm is older than the replacement age, replace the alarm.
    • Go to the section about replacement.
    <1m

Identify the signal from the alarm

Estimated 2 min

End-of-life signal pattern
Unverified — do not rely on this value
CONSULT THE DOCUMENTATION FOR YOUR ALARM

No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.

Permitted battery type
Unverified — do not rely on this value
CONSULT THE DOCUMENTATION FOR YOUR ALARM

No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.

Battery replacement interval for a replaceable battery
Manufacturer or standard verified
1 year

Source: CO Alarms · tier 1 · accessed 2026-07-29

  1. If the alarm has a replaceable battery, install a new battery.
    • Use only a battery type that the manufacturer specifies.
    • Make sure that the battery terminals agree with the polarity symbols.
    1m
WARNING

REPLACE AN ALARM THAT CONTINUES TO GIVE A SHORT SIGNAL.
An alarm at the end of its life does not sense carbon monoxide.

  1. If the short signal continues after you install a new battery, replace the alarm.
    • An end-of-life signal does not stop when you install a new battery.
    <1m
  2. If the alarm has a digital display, read the code on the display.
    • The documentation for your alarm gives the meaning of each code.
    • If the display shows a number, go outside and call 911.
    <1m

Replace the alarm

Estimated 6 min to 10 min

NOTEMake sure that the new alarm has the mark of a recognized test laboratory. CPSC says to put an alarm on each level of the home and outside each sleeping area.
Alarm locations in the home
Manufacturer or standard verified
One on each level of the home, and one outside each sleeping area

Source: CO Alarms · tier 1 · accessed 2026-07-29

  1. Install the new alarm in agreement with the documentation of the manufacturer.
    • CPSC says to install an alarm on each level of the home.
    • CPSC says to install an alarm outside each sleeping area.
    • CPSC says not to install an alarm in an attic or a basement without a sleeping area.
    5m
  2. Push the test button until the new alarm makes a loud sound.
    • The test button shows that the circuit operates.
    • The test button does not show that the sensor is accurate.
    <1m
  3. Release the test button.
    <1m

After the job

Estimated 4 min

Alarm test interval
Manufacturer or standard verified
1 month

Source: CO Alarms · tier 1 · accessed 2026-07-29

  1. Write the date of installation on the new alarm.
    <1m
  2. Write the replacement age of the new alarm in your records.
    <1m
  3. Make a monthly reminder for a test of the alarm.
    1m
  4. Discard the old alarm in agreement with the local rules.
    1m

Terminology

This page uses one term for each item and holds it throughout, as ASD-STE100 requires. Equipment sellers and other guides use the names below for the same parts.

carbon monoxide alarm
Also called: CO alarm, carbon monoxide detector, CO detector, CO2 detector, carbon monoxide sensor, monoxide detector
end-of-life signal
Also called: end of life beep, chirping, beeping every 30 seconds, carbon monoxide detector keeps beeping, END code, ERR code
date of manufacture
Also called: manufacture date, date code, expiry date, expiration date
replacement age
Also called: lifespan, life expectancy, how long do CO detectors last, shelf life

When to use a professional

Stop this procedure if the alarm gives a continuous loud signal. Move all persons outside to fresh air. Call 911 from outside the home. Do not look for the source of the carbon monoxide. Do not go into the home again until the responders permit it.

Speak to a qualified technician if the alarm gives an alarm signal again after the responders permit entry. A qualified technician must examine each appliance that burns gas or oil. The same is necessary for each appliance that burns wood or charcoal. A qualified technician must also examine the chimney and the vents. This page cannot find the source of carbon monoxide and it does not try.

Stop if the alarm has wires. Do not remove the mounting plate. Do not disconnect the wires. A qualified electrician must do all work behind the mounting plate.

Common questions

How long does a carbon monoxide detector last?

There is no single answer and this page refuses to invent one. CDC says to follow the manufacturer's instructions or to replace the detector every five years. Kidde says its own alarms have a proven life of seven to ten years, that everything it made from 2013 is a ten-year unit, and that anything older is a seven-year unit. CPSC gives no universal number and says the recommended replacement age comes from the product literature or from the manufacturer. Averaging five, seven and ten would produce a number that no authority actually stands behind, so read the figure on your own alarm and in its manual.

Why is my carbon monoxide detector beeping every 30 seconds?

It is a maintenance signal rather than an alarm, but which one depends on the model. A short repeated chirp usually means low battery first and end of life second, and the way to tell them apart is to fit a fresh battery: if the chirp stops it was the battery, and if it carries on the alarm has reached the end of its life. The interval that means what is set by the manufacturer, not by any standard, so the exact pattern for your unit is in your manual. What matters is that an alarm in end-of-life mode is no longer detecting anything.

My CO alarm is going off right now. What do I do?

Get everyone outside into fresh air immediately and call 911 from outside. CPSC says not to try to find the source of the carbon monoxide, to do a head count once you are out, and not to go back in until the emergency responders give you permission. Carbon monoxide has no smell and no colour, and CDC notes that people who are asleep or impaired can die from it before they ever notice symptoms. Treat a sounding CO alarm as an evacuation, not as a troubleshooting exercise.

Is a CO2 detector the same as a carbon monoxide detector?

No, and this is a common and dangerous mix-up. Carbon monoxide is CO; carbon dioxide is CO2 and is a different gas with different detectors, usually sold for greenhouses, breweries and ventilation monitoring. A CO2 monitor will not warn you about carbon monoxide. A smoke alarm will not either, unless the unit is a combination smoke and CO alarm, which CPSC notes are sold.

Can I take the battery out to stop the beeping?

No. An alarm with no battery is not protecting anyone, and carbon monoxide is exactly the hazard you cannot detect for yourself. If the noise is a low-battery chirp, fit the battery the manufacturer specifies. If it is an end-of-life signal, the unit needs replacing and no battery will silence it.

Where should carbon monoxide alarms go in the house?

CPSC says to install CO alarms on each level of the home and outside sleeping areas, and not to put them in attics or basements unless those contain a sleeping area. CDC gives the same placement near every sleeping area. Beyond that, follow the installation instructions supplied with your alarm, because minimum and maximum distances from appliances vary by model and some units are not meant for every room.

Sources

Every specification on this page is traced to one of these sources. Tier 1 is a manufacturer document, a published standard, or a government safety authority. See Standards for the full tiering rule.

  1. Tier 1Carbon Monoxide Fact SheetU.S. Consumer Product Safety Commission · accessed 2026-07-29 · re-verification due 2027-01-25
  2. Tier 1CO AlarmsU.S. Consumer Product Safety Commission · accessed 2026-07-29 · re-verification due 2027-01-25
  3. Tier 1Carbon Monoxide Poisoning BasicsCenters for Disease Control and Prevention, National Center for Environmental Health · accessed 2026-07-29 · re-verification due 2027-01-25
  4. Tier 1When Should I Replace My Carbon Monoxide Alarm?Kidde (Carrier Global Corporation) · accessed 2026-07-29 · re-verification due 2027-01-25
  5. Tier 1How to Find the Date of Manufacture on an AlarmKidde (Carrier Global Corporation) · accessed 2026-07-29 · re-verification due 2027-01-25
  6. Tier 1When Should I Replace My Alarms?Kidde (Carrier Global Corporation) · accessed 2026-07-29 · re-verification due 2027-01-25
  7. Tier 1Keeping Your Community Safe with Carbon Monoxide AlarmsNational Fire Protection Association · accessed 2026-07-29 · re-verification due 2027-01-25

Revision history

Current version 1 · updated 2026-07-29 · next review due 2027-07-29

  1. v1 · 2026-07-29First draft. Evacuation boundary and test-button limits from the CPSC carbon monoxide fact sheet. Service life published as a recorded disagreement between CDC, CPSC and Kidde rather than as a number.

Corrections to this page are listed in the public corrections log. Reports that are credible and not yet verified are listed in the public errata register, and an open one renders above the step it concerns.

Comments and corrections

Found an error? A correction with a manufacturer source is applied and logged publicly. You can also write to corrections@fixchecklist.com.

Every step above carries its own report control, which tags the report with that step so a correction reaches the right place. For anything about the procedure as a whole — the order of the sections, a step that is missing, something that did not match your equipment — use this: report something about this whole procedure.

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