This is a great question. And ultimately, no matter what advice you get from others on the internet, you should always check your manual first for your specific model of CO detector to help identify what the issue might be. If you don’t have the manual for whatever reason, you can find a copy with a quick search online.
That out of the way, if you’re 100% sure it’s not due to the presence of carbon monoxide, it’s likely one of a few things:
- Low voltage to the detector
- It expired
This. And you might as well replace the unit anyways since it expires this year.