First Alert Smoke/CO Detectors
First Alert Detectors model 9021B were installed in August 2018, during renovation. The manufacture date on the one from the hallway is June 26, 2018. On 7/25/2025 replaced them with model SC9120BA.
7/26/2025 – New unit in the Office began 3-chirps evey minute. Called First-Alert and they are sending a replacement that will have a different model number as the ones we have are for Canada. He would not replace the other three. The units have a 10-year warranty.
Most CO alarms expire after 7 years. Our CO Alarms use electrochemical sensors precisely calibrated to determine PPM levels of CO in the air. These sensors degrade naturally over time and after about 7 years are no longer precise enough to be reliable in detecting exact PPM levels, leading to false alarms or not being able to detect elevated CO levels. From their web site here.
Refer to the chart to learn what “chirps” or “beeps” mean on CO alarms. Troubleshoot 1 chirp, 3 chirps, 5 chirps, or something different. From here.
| Chirp Pattern | This means… | You should… |
| The horn chirps 1x per minute. | Low battery warning. | Install a new Duracell, Energizer, or Everready battery. |
| The horn sounds 3 chirps every minute. | Malfunction warning. CO alarm needs to be replaced. | Alarms under warranty should be returned to manufacturer for replacement. |
| The horn sounds 5 chirps every minute. | End of life signal. CO alarm needs to be replaced. | Immediately replace the alarm. |
To determine which Smoke/CO Alarm initiated an alarm.
During an Alarm:
On Initiating Alarm(s) – Red LED(s) flashes (flash) rapidly
On All Other Alarms – Red LED is Off
After an Alarm (Latching):
On Initiating Alarm(s) – Green LED(s) On, Red LED(s) flash once every 5 seconds
On All Other Alarms – Green LED(s) On, Red LED(s) is O
How to Replace a 9V Battery
- Use the plastic tab to gently open the battery compartment.
- Remove the old battery.
- Look at your 9V battery to identify the positive (+) and negative (-) contacts similar to what is shown in the image. When installing the battery in your alarm make sure they match the same polarity in the battery drawer. Note: the negative side has a larger opening in the back of the battery drawer so it will only fit one way without forcing it closed.
- Insert the new battery into the compartment with the positive (circular ? ) contact closest to the center of the detector. The negative (hexagonal ? ) contact should be closer to the outside of the detector.
- Gently close the battery compartment. If it won’t close, the battery may be facing the wrong direction.
The image below is from the O&M info that is in DropBox/O&M Manuals that can be accessed via this link.
