Electrical guide
Smoke or CO detector chirping: why, and how to make it stop
By the Home Doctor team · Reviewed
Quick answer
A smoke or carbon monoxide (CO) detector that chirps once every 30 to 60 seconds usually needs a new battery. If it keeps chirping with a fresh battery, check the manufacture date on the back: smoke alarms should be replaced 10 years after that date, and many chirp at end of life. A battery costs a few dollars and a new alarm about $15 to $80. A loud, repeating alarm is different: treat it as real, and if it's a CO alarm, get everyone outside and call 911.
- How urgent
- Urgent
The chirp itself isn't dangerous, but an alarm that's chirping may not be able to warn you. Fix it today or tomorrow, not next month.
- DIY or pro
- DIY
Changing a battery or a whole alarm is a DIY job with a step ladder. Hardwired alarms usually plug into a connector. If the wiring needs changing, call an electrician.
Stop and call a pro now if
- A CO alarm is sounding a full alarm (on most newer models, four beeps and a pause, repeating): get everyone, including pets, outside and call 911 or the fire department from outside. Don't go back in until they say it's safe.
- A smoke alarm is sounding a full alarm (usually three beeps and a pause, repeating) and it isn't clearly from cooking: get everyone out and call 911 from outside.
- Anyone has a headache, dizziness, nausea or confusion that eases outdoors, especially several people at once: get out and call 911, even if no alarm is sounding.
Common causes and how to tell them apart
1. Low battery
- How to tell
- One short chirp every 30 to 60 seconds from one alarm. It often starts in the middle of the night, when the house is coolest and a weak battery has the least to give.
- What fixes it
- Replace the battery with the type printed on the alarm. Hardwired alarms have a backup battery too.
2. End of life
- How to tell
- It keeps chirping with a fresh battery, or it has a sealed battery that can't be changed. A smoke alarm's manufacture date is 10 or more years ago, or a CO alarm is past its replace-by date.
- What fixes it
- Replace the whole alarm. It can't be fixed.
3. Leftover low-battery warning
- How to tell
- It started or kept chirping right after you changed the battery.
- What fixes it
- Make sure the battery is the right type, fully seated, and the drawer is closed. Take the battery out, hold the test button for about 15 seconds, then put it back and press Test.
4. Fault or dirty sensor
- How to tell
- A different chirp pattern, a flashing error light, or false alarms with no smoke.
- What fixes it
- Vacuum the vents gently. The label on the back explains the light and chirp codes. If the fault continues, replace the alarm.
5. It's a different device
- How to tell
- The chirp continues after you've changed the battery. Chirps echo and are hard to place, and CO alarms, other smoke alarms, and battery-powered thermostats or security sensors can chirp too.
- What fixes it
- Stand under each alarm and wait for the chirp before you change anything else.
Not sure which one you have?
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What you can safely try first
- 1Make sure it's a chirp, not an alarm. A chirp is one short beep every 30 to 60 seconds. An alarm is loud and doesn't stop.
- 2Find the chirping unit by standing under each alarm and waiting.
- 3Check the date on the back. A smoke alarm 10 or more years old needs replacing, not a new battery.
- 4Replace the battery with the type printed on the alarm. For a hardwired alarm, switch off its breaker and unplug it from its connector first.
- 5With the battery out, hold the test button for about 15 seconds. Then put the new battery in and press Test.
When to call a pro
- A hardwired alarm keeps chirping after a new battery and a new alarm.
- You're switching to a different brand of hardwired alarm and the connector doesn't match.
- The alarms are on ceilings you can't safely reach.
- A CO alarm has gone off. Have a licensed HVAC tech inspect fuel-burning appliances before you use them again.
What it costs
| Job | DIY parts | Pro, installed |
|---|---|---|
| Replace a 9-volt or AA battery | $3–$10 | — |
| Replace a battery-only smoke alarm | $15–$50 | $75–$200 |
| Replace a hardwired smoke alarm (same connector) | $25–$60 | $100–$300 |
| Replace with a combination smoke and CO alarm | $30–$80 | $100–$300 |
| Add a new hardwired, interconnected alarm | Not recommended | $200–$500 |
Ballpark US ranges as of September 27, 2026. Your region, access and the specifics of your home can move these a lot. Get two or three quotes for anything over a few hundred dollars.
What to tell the pro
I have [number] [hardwired / battery-only] [smoke / CO / combination] alarms. The one in the [location] keeps chirping [every 30 to 60 seconds / in a different pattern]. I've [replaced the battery / held the test button / replaced the alarm] and it still chirps. They're about [age] years old, [interconnected / separate], and the ceilings are about [height]. Can you replace them, and does your price include the alarms?
Questions people ask
Why is my smoke detector still chirping after I changed the battery?
Usually one of three things: the alarm is past its 10-year life, the new battery isn't seated or is the wrong type, or the alarm is holding on to the low-battery warning. Take the battery out, hold the test button for about 15 seconds, and put it back. If it still chirps, check the date on the back and replace the alarm.
How do I tell a chirp from a real alarm?
A chirp is a single short beep every 30 to 60 seconds and means the alarm needs attention. A real alarm is loud and keeps going. Most newer smoke alarms sound three beeps and a pause, and CO alarms sound four beeps and a pause. Treat any full alarm as real until you know otherwise.
How long do smoke and CO detectors last?
Replace smoke alarms 10 years after the manufacture date printed on the back. CO alarms typically last 5 to 10 years depending on the model, and many print a replace-by date on the label. Press Test on every alarm once a month.
What should I do if my CO alarm goes off?
Get everyone, including pets, outside into fresh air right away, and call 911 or the fire department from outside. Don't go back in until they say it's safe, even if the alarm stops. Carbon monoxide has no color or smell, so the alarm may be your only warning.
Get an answer for your house
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General guidance, not a substitute for a licensed professional who can see the problem in person. If you smell gas, see sparks or smoke, or anyone is hurt, leave the area and call 911.