Smoke and carbon monoxide alarm check: do it when the clocks change

When you change the clocks, check your alarms. It takes five minutes, and it's the habit fire departments and the CDC recommend twice a year.

Reviewed October 2026

The five-minute check

1. Press the test button on every smoke alarm. It should sound loud enough to wake you from any bedroom. NFPA advises testing at least once a month, so this is the minimum.
2. Change the batteries in any alarm that takes replaceable batteries. NFPA says at least once a year; the CDC says to check or replace CO alarm batteries every time the clocks change.
3. Check the date on the back. Replace smoke alarms 10 years from the date of manufacture. Carbon monoxide alarms wear out too: replace them on the date the maker gives, usually printed on the alarm.
4. Sealed-battery alarm chirping? Replace the whole alarm. If a replaceable-battery alarm chirps, just change the battery.
5. Test your carbon monoxide alarms the same way, with the test button.

Do you have enough alarms?

Smoke alarms belong, according to NFPA:

• inside every bedroom
• outside each sleeping area, such as the hallway outside the bedrooms
• on every level of the home, including the basement

Mount them on the ceiling or high on a wall. For the best protection, interconnect them so that when one sounds, they all do. That matters most if you sleep with bedroom doors closed.

Carbon monoxide alarms should be on every level and outside sleeping areas, and the CDC recommends one with a battery or battery backup so it works in a power outage, which is exactly when generators and heaters cause CO poisoning.

Which kind of smoke alarm?

Ionization alarms react faster to flaming fires; photoelectric alarms react faster to smoldering fires and give fewer false alarms near kitchens and bathrooms. NFPA recommends having both types, or dual-sensor alarms.

If an alarm goes off

• Smoke alarm: get outside and stay outside. You may have as little as two minutes to get out once it sounds. Call 911 from outside.
• Carbon monoxide alarm: leave right away and call 911. If anyone feels dizzy, light-headed or sick to their stomach, tell the dispatcher. More than 400 Americans die each year from carbon monoxide poisoning not linked to fires.

While you're at it, check your emergency kit: swap out expired food, water and medicine, and test the flashlights.