Normal operation · First Alert · smoke

First Alert: Green flash once a minute, no sound

Normal operation: the SM210L’s power LED flashes green once every minute and the horn is silent.

What you see: One green flash about every 60 seconds
What you hear: Silent

If it is sounding a full alarm instead: the maker’s emergency instruction

Smoke alarm

First Alert (SM210L manual): if the alarm sounds, get everyone out of the house immediately — do not stop to dress or collect anything. Feel doors with the back of your hand and do not open a hot one; cover your nose and mouth with a damp cloth; meet at your planned place outside and count heads; call the fire department from outside, giving your address and then your name; never go back inside a burning building.

From User’s Manual — Smoke Alarm, 10-Year Sealed Battery with Escape Light.

The First Alert alarm on these pages senses smoke only. For a carbon monoxide alarm, follow its own maker’s instruction.

What First Alert says to do about this signal

Nothing to do. First Alert says to test the alarm every week with the Test/Silence button.

From User’s Manual — Smoke Alarm, 10-Year Sealed Battery with Escape Light. If your alarm’s pattern is not exactly this, check the manual for your model: First Alert models do not all use the same signals.

Other First Alert signals

Normal operation on other brands

The same state sounds and looks different on each make — which is why a chirp pattern cannot be read without the brand.

Sources

Every line on this page comes from First Alert’s own documents, read on the date shown. Nothing is taken from third-party code sites or other makes.

First Alert (BRK Brands): User’s Manual — Smoke Alarm, 10-Year Sealed Battery with Escape Light — Model SM210L. support.firstalert.com Checked 2026-09-29.