Wondering what's going on in there?
How a smoke alarm works, in plain English
A smoke alarm is a small sensor with a loud speaker. It watches the air all the time and runs checks on itself. When something's wrong with the alarm, not the air, it chirps.
- Power. Hardwired alarms plug into house power in the ceiling. A green light shows it's getting power.
- The sensing chamber. Air drifts into the middle. When smoke gets in, the alarm sounds.
- The battery. Battery alarms run on it. Hardwired ones keep it as a backup for power outages.
- The Test button. Holding it checks the speaker and, on many models, resets the alarm.
- The light. It blinks to show the alarm is working. Patterns differ by brand, so check the manual for yours.
So a chirp usually means one of these:
- The battery is low, the wrong type, or not seated.
- It needs a reset after a battery change, or the vents are dusty.
- The alarm is worn out. Makers say about 10 years.
- A hardwired alarm lost house power.
A loud alarm that keeps going is different. That's the alarm doing its job.
Have a smoke and CO combination alarm? Use our carbon monoxide guide.
Rather not do it yourself? Call an electrician.
That's a fine choice. Maybe you're busy. Maybe you're selling the house and just want it done right. An electrician can replace a wired alarm or fix one that has no power. If it's a real fire alarm, get everyone out and call 911 first.
Most electricians charge $50–$130 an hour, and many charge a $100–$200 service call that covers the first hour.
Find electricians near you
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What to say
Calling a pro? Here's what to say.
A few lines to read when they pick up, and the questions to ask before anyone comes out.
Before you call
Say this
Hi. My smoke alarm keeps beeping, and I need it checked or replaced. When's the soonest you can get here? And what's your fee for the visit? Does it go toward the repair?
Always ask
- What's your fee to come out, and does it cover the first hour?
- Do you charge by the job or by the hour?
- Will you tell me the full price before you start any work?
Watch out if
- They push rewiring the whole house on the first visit for a small problem.
- They can't show you a license number.
- They won't give you a price before starting.
Feeling pushed to decide on the spot? You can say no and hang up. You owe nothing for a phone call.
Answer up to 5 quick questions. We'll give you the words a pro uses.
Answer the questions →More of a list person?
Common sounds, causes, tests and costs
Find the row that sounds like your alarm. The quick test is something you can check yourself in a few minutes.
| What you notice | What it probably is | Quick test | Do it yourself | With a pro | Verdict |
|---|---|---|---|---|---|
| Loud alarm that keeps going, or all alarms sounding | Treat it as a real fire | None. Get out | Pro job | $100–$200 | CALLSee the answer: Treat it as a real fire |
| Loud alarm right after cooking or a hot shower | Smoke or steam set it off | Clear the air and see if it stops | Free | Not needed | FIXSee the answer: Smoke or steam set it off |
| Chirps every 30–60 seconds | The battery is low | Put in a new battery | Free | Not needed | FIXSee the answer: The battery is low |
| Chirps; the drawer won't close or the battery is loose | The battery isn't sitting right | Check the battery type, the + and − marks, and the drawer | Free | Not needed | FIXSee the answer: The battery isn't sitting right |
| Still chirps after a new battery | Leftover charge, or dust in the alarm | Battery out, hold Test 15 seconds, then vacuum the vents | Free | Not needed | FIXSee the answer: Leftover charge, or dust in the alarm |
| Chirps after a new battery; over 10 years old, or a sealed alarm | The alarm is worn out | Check the date on the back | $10–$35 | Not needed | FIXSee the answer: The alarm is worn out |
| Hardwired; chirps after a new battery and a reset, or over 10 years old | The hardwired alarm is worn out | Check the date and the brand on the back | $30–$50 | $70–$150 | FIXSee the answer: The hardwired alarm is worn out |
| Hardwired; chirps, green power light off | The alarm isn't getting power | Look for the green power light | Pro job | $100–$200 | CALLSee the answer: The alarm isn't getting power |
| Chirping alarm on a high ceiling | Get help reaching it | None. Get help | Pro job | $100–$200 | CALLSee the answer: Get help reaching it |
2026 U.S. averages, rounded. Pro prices include parts and labor. Most electricians charge $50–$130 an hour, and many charge a $100–$200 service call that covers the first hour. Nights, weekends and big cities cost more. See all repair prices
Want proof it's working?
The Test button check
Once the chirping stops, make sure the alarm still does its real job.
- Hold the Test button until the alarm sounds. It should be loud, then stop when you let go.
- If your alarms are connected, the others should sound too.
- Do this once a month.
- Loud and clear: it's working.
- Weak, or nothing: put in a new battery and try again. Still weak? Replace the alarm.
- The others don't sound: on hardwired, connected alarms, have an electrician check the wiring.
Not sure it's safe to stay?
Get out right away if…
- The alarm goes off loud and keeps going, and you can't see an obvious cause.
- You smell smoke or burning, or see smoke.
- The alarm or the ceiling around it is hot, scorched or melting.
- A carbon monoxide alarm is sounding. It may look like a smoke alarm. Read the label.
Get everyone out, pets too, and call 911 from outside. Never take out the battery to stop a chirp and leave it out. An alarm with no battery can't warn you.
Got a big repair quote?
Should you replace it?
Smoke alarms aren't repaired. They're replaced. A new battery alarm costs about $10–$35, according to Fixr. A hardwired one costs about $30–$50, or $70–$150 installed by a pro, according to Fixr. Ask yourself three things:
- How old is it? Makers say to replace smoke alarms about 10 years after the date on the back.
- Are the others the same age? If one is worn out, the rest probably are too. Replacing them together saves trips up the ladder.
- Hardwired? A replacement that plugs into the same connector is a 30-minute job. New wiring is a job for an electrician.
Example: a 12-year-old alarm that chirps with a new battery should be replaced. If it was put in with the house, the others are 12 years old too.
Ran into a word you don't know?
Smoke alarm words, explained
Tap through these before you go looking. The drawings show roughly what each part looks like.
- Smoke alarm
- The round device on the ceiling that sounds when it senses smoke. People also call it a smoke detector.
- Chirp
- One short beep, then quiet. It means the alarm needs attention, not that there's smoke.
- Test button
- The button on the front. Hold it to check the alarm. On many models it also resets it.
- Hush button
- A button that quiets a false alarm for a few minutes. On some alarms it's the same as the Test button.
- Battery drawer
- The slot on the back or side that holds the battery. It has to click shut.
- 10-year sealed alarm
- An alarm with a battery built in for its whole life. You can't change the battery. You replace the whole alarm.
- Hardwired alarm
- An alarm that runs on house power through a plug in the ceiling. It keeps a battery as a backup.
- Connector (pigtail)
- The plug that hangs from the ceiling and snaps into a hardwired alarm.
- Power light
- A small light, often green, that shows a hardwired alarm is getting house power.
- Date label
- The sticker on the back with the date it was made. Replace the alarm about 10 years after it.
- Breaker
- A safety switch in your home's breaker box (the gray metal panel). It cuts power to part of the house.
- Sturdy step stool or ladder
- Something steady to stand on. Never a chair or the top step.
Still have questions?
Questions people ask most
Why is my smoke detector beeping?
A single chirp every 30 to 60 seconds usually means a low battery. If it still chirps with a new battery, it may need a reset, or it may be worn out. A loud alarm that keeps going means it sensed smoke. Get out and call 911.
Is a beeping smoke detector an emergency?
A single chirp every 30 to 60 seconds is not an emergency; it usually means a low battery. A loud alarm that keeps going is. Get everyone out, pets too, and call 911 from outside. A carbon monoxide alarm can look like a smoke alarm, so read the label before you decide it's a false alarm.
How do I tell which smoke alarm is beeping?
To find the alarm that's chirping, stand under each one and wait for the next chirp, which comes every 30 to 60 seconds. Check the date on the back of each one too, since an alarm over 10 years old chirps when it's worn out. If connected alarms are all sounding loud, get out and call 911 first.
Why does it still chirp after I changed the battery?
A smoke detector that still chirps after a battery change may have the wrong battery, a battery in backward, or a drawer that didn't click shut. If those are fine, reset it: battery out, hold Test for 15 seconds, battery back in. If it's over 10 years old, replace it.
Why does a hardwired smoke alarm beep with no battery?
A hardwired smoke alarm can beep with no battery because it still runs on house power, and many hold leftover charge. Kidde says to turn off its breaker, unplug the alarm from its connector, and take the battery out. Then hold Test for at least 15 seconds, and put in a fresh battery. If it still chirps, the alarm may be worn out.
Why does my smoke detector only beep at night?
A smoke detector often chirps at night because a weak battery struggles more as the house cools. Kidde says most homes are coolest between 2 and 6 a.m., and that drop can push a fading battery into low-battery chirps. Replace the battery, even if the alarm seems fine during the day.
How do I stop a smoke detector from beeping? Will it stop if I pull the battery?
To stop a chirp, put in a new battery and hold Test. For a false alarm from cooking, clear the air and press Hush if it has one. Pulling the battery doesn't always stop it, because a hardwired alarm still has house power and leftover charge. And an alarm without a battery can't warn you. The U.S. Fire Administration says a missing battery is the same as having no alarm.
What does it mean when my smoke detector beeps once, twice or 3 times?
One chirp every 30 to 60 seconds usually means a low battery, Kidde says. Other beep patterns differ by brand and model, so check the label or manual for yours. A loud alarm that repeats over and over means smoke. Get out and call 911.
How often should smoke alarms be replaced?
Replace smoke alarms about every 10 years from the date on the back, makers like First Alert say. Sealed 10-year alarms chirp when it's time.
Do I need an electrician to replace a hardwired smoke alarm?
You don't need an electrician to replace a hardwired smoke alarm if the new one plugs into the same connector. Turn the breaker off first. If the plug doesn't match or you see bare wires, call an electrician.
Why do all my smoke alarms go off at once?
All your smoke alarms go off at once because hardwired alarms are often connected: when one senses smoke, they all sound. Get out first and call 911. Once firefighters say it's safe, an electrician can find which one started it.
Who do I call for a beeping smoke detector?
Most beeping smoke detectors don't need a pro: a new battery, a reset or a new alarm fixes them. Call an electrician if a hardwired alarm has no power, the new alarm's plug doesn't match, or you see bare wires. If an alarm sounds and you smell smoke, get out and call 911.
How we built this
The questions follow the order makers like Kidde and First Alert give for a chirping alarm: the kind of sound, the kind of alarm, its age, the battery, then a reset and cleaning. Each answer makes some causes more likely and others less likely.
Prices are 2026 national averages from published repair-cost guides, rounded. Your local prices will differ.
- Kidde, what causes consistent chirping (read October 2026)
- First Alert, why is my smoke alarm chirping (read October 2026)
- Fixr, smoke detector installation cost (January 2025)
- HomeGuide, smoke detector installation cost (June 2024)
- HomeAdvisor, cost to hire an electrician (June 2026)
- Kidde, intermittent beeping causes (read October 2026)
- Kidde, nighttime alarm chirps (read October 2026)
- First Alert store, why is my alarm still chirping with a new battery (read October 2026)
- U.S. Fire Administration, smoke alarms (reviewed September 2026)
How we make money: some links go to parts stores that pay us a small commission, and some pro listings pay us when you call them. Verdicts come from the diagnosis, not from who pays more.