Working alarms give your household precious time to get out. Good placement, monthly tests and timely replacement keep them ready.
The essentials
- Install smoke alarms on every level, including the basement, and inside and outside each sleeping area, as the U.S. Fire Administration advises.
- Put carbon monoxide alarms on each level of the home and outside sleeping areas, as CPSC advises.
- Test alarms every month and replace batteries at least once a year, unless the alarm has a sealed 10-year battery.
- Replace smoke alarms 10 years from the manufacture date, and follow the manufacturer’s schedule for CO alarms.
- Interconnected alarms all sound together, so everyone hears a warning wherever it starts.
Smoke alarms and carbon monoxide (CO) alarms are among the cheapest safety equipment in a home, and among the most important. Fire can spread quickly, and carbon monoxide is a gas you can’t see or smell. An alarm is often the first warning you’ll get.
The guidance below comes from the U.S. Fire Administration (USFA) for smoke alarms and the Consumer Product Safety Commission (CPSC) for CO alarms. Always follow the instructions that come with your alarms, too.
Where smoke alarms go
USFA recommends smoke alarms:
- On every level of the home, including the basement
- Inside each bedroom
- Outside each separate sleeping area, such as the hallway or landing outside bedrooms
Mount them on the ceiling or high on a wall, following the manufacturer’s directions for the exact spot. Those directions usually cover how far to keep alarms from kitchens and bathrooms, where cooking smoke and steam can cause false alarms.
Where CO alarms go
CPSC advises installing CO alarms on each level of the home and outside sleeping areas. It notes that they shouldn’t go in attics or basements unless those spaces include a sleeping area.
Combination smoke and CO alarms are widely available and can simplify things, as long as each location still gets the protection it needs.
Choosing alarms
- Power: alarms run on replaceable batteries, sealed 10-year batteries, or household wiring with a battery backup.
- Interconnection: USFA advises choosing interconnected alarms, so that when one sounds, they all sound. That matters in larger homes and with bedroom doors closed.
- Sensor type: USFA recommends having both ionization and photoelectric alarms, or dual-sensor alarms that contain both kinds of sensor.
Test them every month
Both USFA and CPSC recommend testing alarms monthly. Press the test button and hold it until the alarm sounds. Make sure everyone in the house knows what each alarm sounds like and what to do when they hear it.
Pro tip
Tie the monthly test to something you already do, like paying a bill or changing the calendar page. A two-minute walk-through of every alarm is easy to remember that way.
Batteries and replacement
| Alarm | Battery | Replace the whole alarm |
|---|---|---|
| Smoke alarm, 9-volt battery | At least once a year | Every 10 years |
| Smoke alarm, hardwired | Backup battery at least once a year | Every 10 years |
| Smoke alarm, sealed 10-year lithium | Not replaceable | According to the manufacturer’s instructions |
| CO alarm | Annually, if it uses replaceable batteries | According to the manufacturer’s instructions |
USFA notes that smoke alarms should be replaced 10 years from the manufacture date, not the date you installed them. Check the back of each alarm and write the replacement date where you’ll see it.
Never take the battery out of an alarm to stop nuisance alarms from cooking. Fan the smoke away, open a window, or move the alarm if the manufacturer’s placement advice allows.
If an alarm goes off
Smoke alarm: get out and stay out. Agree on a meeting place outside, then call 911 from there.
CO alarm: move everyone, including pets, outdoors into fresh air immediately, and call 911 or the fire department from outside. Don’t go back in until emergency responders say it’s safe.
Safety first
Fuel-burning appliances such as furnaces, water heaters, fireplaces and gas dryers can produce carbon monoxide if they’re damaged or poorly vented. Have them checked by a qualified professional, and never run a generator or grill indoors or in an attached garage.
Put it on your calendar
Alarm checks fit naturally into a seasonal routine. Our fall home maintenance checklist includes them alongside heating and chimney checks, and our guide to cleaning a dryer vent covers another common source of home fires.
Common questions
What’s the difference between ionization and photoelectric smoke alarms?
They use different sensors, and each type detects different types of fires. The U.S. Fire Administration advises having both types in your home, or using dual-sensor alarms that contain both.
Where do I find the manufacture date?
It’s printed on the back of the alarm. Twist the alarm off its base to check it, then note the replacement date somewhere you’ll see it.
My alarm chirps every minute. What does that mean?
A regular chirp usually means a low battery, but on some models it signals that the alarm has reached the end of its life. Check the manual; if a fresh battery doesn’t stop the chirp, replace the alarm.
What should I do if the CO alarm sounds?
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 emergency responders say it’s safe.
Can I install hardwired alarms myself?
Battery-powered alarms are an easy DIY job. Hardwired and interconnected systems involve household wiring, so unless you’re qualified, have a licensed electrician install or replace them.
This guide is general information, not professional advice. Follow the manufacturer’s instructions and your local building codes, and hire a licensed professional for electrical, gas, structural or roofing work.