BRK / First Alert SC9120BA: lights, beeps & chirps explained
Hardwired ionization smoke + CO combo with 9V backup (also SC9120 / SC9120B). Here is what every light and sound on the BRK / First Alert SC9120BA means, how to test and hush it, and when it needs replacing. It's an older model I still find on ceilings across the Lower Mainland. For carbon monoxide protection, see our carbon monoxide alarm installation.
What the lights mean
| Light | Meaning |
|---|---|
| Red CO light flashing with 4 beeps | CARBON MONOXIDE detected. |
| Green, 2 s on / 2 s off | Low-battery chirp has been silenced (up to 8 hours). |
What the beeps and chirps mean
| Sound | Meaning |
|---|---|
| 3 beeps, pause, repeat | SMOKE. Get everyone out and call 911. |
| 4 beeps, pause, repeat | CARBON MONOXIDE. Get into fresh air and call 911. |
| 1 short chirp a minute | Low battery. Replace the 9V. |
Want to hear them? The free app's sound library plays each pattern.
How to
Test it
Press and hold Test/Silence until it sounds.
Battery
9V alkaline. A new battery does not stop an end-of-life signal.
End of life
10-year life for the alarm and CO sensor. If it keeps chirping with a fresh battery, replace it.
How long does it last?
Replace it 10 years after the date printed on the back. The test button can still work after the sensor has worn out, so the date is what counts. Sometimes the date is on the side, but the back is the best place to look. Need one swapped? See smoke alarm replacement and repair.
What replaces it
Today's replacement is the BRK / First Alert SC6W10A ($94.99 installed, plus the $99.99 service fee).
Other alarm guides
BRK / First Alert SC6W10A · BRK / First Alert SM6W10A · BRK / First Alert 9120BA · BRK / First Alert 9120LBL · BRK / First Alert SC9120LBL · BRK / First Alert 7010BA · BRK / First Alert SC7010BA
All alarm guides · Chirp codes: Kidde vs First Alert