Chirp every 30 to 60 seconds (smoke or CO alarm)
The alarm reporting on itself, not on smoke or carbon monoxide: most often a low battery, and on some alarms the end of the alarm’s working life.
The pattern One short chirp, then silence for 30 to 60 seconds before the next. The clip plays one chirp.
Synthesised from makers’ descriptions; real alarms are much louder and the pitch varies by model. A synthesised clip, not a recording. The sound alone (WAV)
Easily confused with
How to read it
A chirp is one short sound, repeated every 30 to 60 seconds, where an alarm for smoke or carbon monoxide is a repeating set of beeps. On the smoke alarm CPSC staff examined, the low-battery signal to the horn was a pulse about 10 milliseconds wide. No standard sets the chirp: each maker sets its own, and the alarm’s manual lists them. NFPA’s Fire Prevention Week tip sheet gives the common reading: a single chirp every 30 or 60 seconds means the battery is low, and chirping that continues after the battery has been replaced means the alarm is at the end of its life. CO alarms also have end-of-life sounds that vary by manufacturer, the tip sheet says.
Also searched as: co detector chirping, end of life chirp, low battery chirp, smoke alarm chirp, smoke detector beeping every 30 seconds, smoke detector chirping.
These describe what each alarm sound means and which standard sets it. Sounds differ between makers and models, and the alarm’s own manual lists what each of its sounds means. What to do when an alarm sounds is set out by the US Fire Administration at usfa.fema.gov and by your local fire department.
What each maker’s chirps mean
| Alarm | Low battery | End of life | Other chirps |
|---|---|---|---|
| Kidde smoke alarms | A chirp every 30 to 40 seconds (every 60 on some) for at least seven days | Sealed-battery models: a chirp every 30 seconds | Hush: a chirp every 30 to 40 seconds for about seven minutes |
| Kidde CO alarms | A chirp once every 60 seconds | A chirp every 30 seconds, from seven years after first power-up | Not given |
| BRK CO and combination alarms | Not given | 5 chirps, after about 120 months (60 or 72 on some models) | Not given |
| Gentex S1209 smoke alarm | 1 chirp | Not given | 2 chirps: silenced for smoke, or a trouble condition |
| Gentex CO1209 CO alarm | 1 chirp with an LED flash | 3 chirps with an LED flash | 2 chirps with an LED flash: dirty or defective, or a large influx of CO |
Kidde’s sealed-battery smoke alarms and its CO alarms chirp every 30 seconds at the end of their life, the same interval Kidde gives for some low-battery chirps. BRK says its end-of-life chirp can be silenced for about 2 days at a time, and after about 2 to 3 weeks can’t be silenced.
The clip on this page
It plays one chirp of 10 milliseconds at 3.2 kHz, the frequency CPSC staff measured on a smoke alarm’s horn; a real alarm repeats it every 30 to 60 seconds. UL 217 sets no frequency for the horn, so a real chirp may sound higher or lower.
Read next
- Next in Smoke and CO alarm soundsLow-frequency 520 Hz alarm (sleeping rooms)A fire alarm in a sleeping room that sounds a low buzz in place of a high-pitched beep. It is the three-beep fire alarm rhythm at 520 Hz, which NFPA 72 requires of alarms provided to wake people in sleeping areas.
- The same shape in African flagsFlag of TanzaniaTanzania’s flag is divided diagonally by a black band edged in gold, from the bottom corner by the pole to the top corner at the fly, with green above and blue below. Tanzania’s Daily News explains the green as vegetation and fertile land, the black as the people, the gold as the country’s natural wealth and the blue as its lakes, rivers and ocean.
More smoke and CO alarm sounds
The same shape elsewhere
Browse symbols drawn with lines.
Sources
- Learn the Sounds of Fire Safety: Fire Prevention Week tip sheet, Fire Prevention Week 2021, ©2021 NFPA, National Fire Protection Association (copy published by Bloomfield Township, Michigan), Smoke alarms; Carbon monoxide (CO) alarms
- What Causes Consistent Chirping?, Kidde support article, Kidde, smoke alarms; carbon monoxide alarms
- How Long Do Smoke and CO Alarms Last?, BRK Installer Corner, BRK Brands, CO and combination alarms
- S1209 Series Photoelectric Smoke Alarm: Installation Instructions and Owner’s Manual, S1209 owner’s manual, Gentex Corporation, test button function; checkout and troubleshooting
- CO1209 Series Carbon Monoxide Alarm: Installation Instructions and Owner’s Manual, CO1209 owner’s manual, Gentex Corporation, checkout and troubleshooting
- Possible Technologies for Improving the Audibility of Residential Smoke Alarms, CPSC-ES-0505 (September 2005), U.S. Consumer Product Safety Commission, §2.3; wireless circuit
Researched, edited and approved by Rory Hansen before publishing. Last reviewed October 9, 2026. How we research
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