Why does my CO alarm keep chirping?

Either a low battery or the sensor itself is at end of life (typically 7 years). The alarm should print a "Replace By" date.

Can I use any 9V battery?

Lithium 9V lasts ~2× alkaline and performs better in cold. For sealed 10-year alarms, you don't replace the battery at all — you replace the whole unit.

Do smoke alarms work during a power outage?

Hardwired alarms have a battery backup — test it monthly. Battery-only alarms work independently.

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Replacement Batteries for Smoke and CO Alarms

Smoke and CO alarms chirp when batteries drop below threshold — but if they fail silent during a blackout, they can miss a generator-induced CO event. Replace every 6 months regardless of chirps.

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Frequently asked

Why does my CO alarm keep chirping?: Either a low battery or the sensor itself is at end of life (typically 7 years). The alarm should print a "Replace By" date.
Can I use any 9V battery?: Lithium 9V lasts ~2× alkaline and performs better in cold. For sealed 10-year alarms, you don't replace the battery at all — you replace the whole unit.
Do smoke alarms work during a power outage?: Hardwired alarms have a battery backup — test it monthly. Battery-only alarms work independently.