Chirp Finder icon

Which smoke alarm is chirping?

0:23Confirmed chirp: every 47 sNext one due in 23 seconds. Stand under the Hallway alarm.

One chirp a minute, bouncing off every ceiling in the house. Chirp Finder hears it, tells you exactly when the next one is due, and measures it under each alarm to find the one that's doing it. Then it tells you whether a battery will fix it.

Coming soon to the App Store

For iPhone and iPad · Works offline · Audio never leaves your phone

Is an alarm sounding continuously? That isn't a chirp. Three long beeps repeating is a fire alarm; four short beeps repeating is carbon monoxide. Get everyone out and call 911. Chirp Finder recognises both patterns and says so, free, but it is not a smoke or CO detector.

👂 Hears the chirp

Listens for the short 3 kHz chirp, confirms it when it repeats, and shows a live countdown to the next one, so the long silence between chirps never looks like nothing is happening. Free.

🎯 Finds the alarm

Stand under each alarm for one chirp. Chirp Finder measures the level at each and ranks them, with a confidence score instead of a guess.

🔋 Battery or replace?

Decodes the pattern (1, 2, 3 or 5 chirps, and how often) against the makers' own manuals, and reads the date off the alarm's back label.

🚨 Fire and CO patterns, free

If it hears a fire (Temporal-3) or carbon monoxide (Temporal-4) alarm pattern, it shows a full-screen warning with a call button. Never behind a paywall.

🏠 My Alarms

Every alarm in the house with its age and replace-by date, and a reminder a month before each one expires.

🔒 Private

Listening, label reading and your alarm list all stay on your iPhone. No account, no ads, no tracking.

Why won't a new battery stop it?

Because it may not be the battery. Smoke alarms are made to be replaced 10 years after the date of manufacture (NFPA 72), and many chirp when they reach it. Since July 2014, battery-powered smoke alarms approved for sale in California have needed a sealed 10-year battery, and New York followed in 2019. The first of those sealed alarms are now reaching their end-of-life chirp, and a battery can't fix that: the whole alarm has to be replaced.

The date of manufacture is printed on the alarm's back label, often as a bare stamp like 2014 Jan. 17. Chirp Finder reads it with the camera and tells you the alarm's age and its replace-by date. Some CO alarms are rated for only 5 or 7 years; for the models in its table, the app uses the maker's own rating.

Not sure what a pattern means on your alarm? See what each chirp means, brand by brand, with links to the makers' manuals.

How it works

  1. Listen. Stand somewhere central and tap Start. After two chirps, Chirp Finder knows the rhythm and counts down to the next one.
  2. Find. Go to an alarm, hold the phone up toward it, and wait for one chirp. Repeat at each alarm. The loudest is the one chirping, and the app tells you how sure it is.
  3. Fix. See what the chirp means for that alarm, scan its label for its age, and follow the steps: a fresh battery, clearing a leftover charge, or a replacement.

No alarm chirping right now? Turn on demo mode to try every step with a simulated alarm.

Pricing

Listening, the countdown and the fire/CO warnings are free, and so is measuring your first alarm and scanning one label. Chirp Finder Pro ranks every alarm, decodes the chirp for your alarm's model, scans every label, and keeps your alarm list, reminders and history: $4.99 a month, or $24.99 a year with a 7-day free trial.