How Often Should You Replace Smoke Detectors in Your Home?
Short answer: replace every smoke detector in your home every 10 years. That's the rule from the U.S. Fire Administration (USFA). Count from the date printed on the back of the alarm, not the day you put it up. Test each one every month. Change the battery at least once a year.
Hardwired alarms wear out too, even though they run on house power. At Cain Electric in Gray Summit, our residential electricians replace and add hardwired smoke and carbon monoxide (CO) alarms all over the St. Louis area.
The clocks just went back on November 1, and the furnace is running again. It's a good week to check yours.
How do you tell how old a smoke detector is?
Look at the back of the alarm for a date. Most alarms have a "made on" date, and many also print a "replace by" date. If the alarm was made more than 10 years ago, replace it.
Here is how to check a hardwired alarm:
- Twist the alarm off its base. Most turn to the left. Let it hang by its wire plug.
- Read the date on the label.
- Twist it back on. The light should come back on.
If you can't find a date at all, the alarm is likely very old. Plan to replace it.
Why do smoke detectors expire after 10 years?
The part inside that senses smoke gets weaker with age, and dust builds up over time. An old alarm can still beep when you press the test button but be slow to notice real smoke. That's why the 10-year rule applies even when an alarm "seems fine."
How often should you change the battery?
Change the battery at least once a year. USFA says to test alarms every month and replace 9-volt batteries at least once a year. Hardwired alarms usually have a backup battery that also needs a new one each year (USFA).
Some newer alarms have a sealed battery that lasts the full 10 years. You don't change that battery. You replace the whole alarm when it's done.
If an alarm keeps chirping after you put in a new battery, it may be telling you it has reached the end of its life. Check the maker's guide or the label on the back.
Where should smoke detectors go?
Put a smoke alarm inside each bedroom, outside each sleeping area, and on every level of the home, including the basement (USFA).
| Spot | Smoke alarm? |
|---|---|
| Inside each bedroom | Yes |
| Hallway outside the bedrooms | Yes |
| Every level, including the basement | Yes |
| Right next to the stove | No, it will go off from cooking |
USFA also says to choose linked alarms, so when one goes off, they all go off. That matters if a fire starts in the basement while everyone is asleep upstairs.
Should smoke detectors be hardwired?
Hardwired alarms that are linked together are the safest setup, and they are the rule for new homes. They run on house power, have a battery backup, and all sound at once. New homes, and many remodels that need a permit, must have alarms set up this way. Your city or county sets the exact rule. Read more in do I need a permit for electrical work in Missouri.
USFA says only qualified electricians should put in hardwired smoke alarms (USFA). The work means adding wire through walls and ceilings and tying it into a circuit.
If your home only has battery alarms, they still work. Just keep up with the testing and batteries. Wireless linked alarms are another choice for older homes where running new wire is hard.
Do you need to replace all of your smoke detectors at once?
If your alarms are linked, it's smart to replace them all at the same time. They are likely the same age, so they will all need it soon. Also, new hardwired alarms have to work with the ones they link to. Mixing brands often doesn't work.
When you replace a hardwired alarm, the new one often comes with a new base and plug. An electrician can swap the base so the new alarm fits and stays linked to the rest.
What about carbon monoxide detectors?
Put a CO alarm on every level of your home and outside sleeping areas (CPSC). CO has no smell and no color. The CPSC says more than 200 people in the U.S. die each year from CO poisoning that isn't from a fire.
Winter is when CO matters most. Furnaces, gas water heaters, fireplaces and generators can all make it. CO alarms wear out too, so check the "replace by" date printed on the back. A combo alarm can sense both smoke and CO in one unit.
If you use a generator when the power goes out, never run it in the house or garage. We cover that in whole home vs portable generators.
When should you call an electrician?
Call an electrician if you want to add hardwired alarms, link the alarms you have, or replace old hardwired alarms that won't stay on. Also call if an alarm on house power keeps losing power, or a breaker trips when you test it.
You should also call if you're adding a bedroom or finishing a basement. That work usually means new alarms need to go in. See electrical work for a home addition.
FAQ
Do hardwired smoke detectors need to be replaced every 10 years? Yes. Hardwired alarms follow the same 10-year rule as battery alarms. House power keeps them on, but the part that senses smoke still wears out.
Is it OK to just pull the battery when an alarm chirps? No. Pulling the battery leaves that room with no alarm. Put in a new battery right away. If it still chirps, replace the alarm.
How often should I test my smoke alarms? Once a month. Press and hold the test button until it beeps. If it doesn't, change the battery and test again.
Can I put in a hardwired smoke detector myself? USFA says only qualified electricians should install hardwired alarms. Swapping a battery alarm is a simple DIY job.
How long do carbon monoxide detectors last? It depends on the model. Read the "replace by" date on the back and replace it on or before that date.
Need new smoke or CO alarms put in?
If your alarms are past 10 years, or you want them hardwired and linked, Cain Electric can help. We serve homes in Gray Summit, Pacific, Washington, Eureka and across the St. Louis area. Learn more about our residential electrical services or call (314) 607-8687 for a free estimate.
