After you replace the battery, the detector should beep to show it's working and then go quiet. But if the detector continues to beep, then it may be that it has reached the end of its life. Typically they expire after 5-7 years and will continue to make the beep no matter what you do. That is because they can no longer detect dangerous levels of carbon monoxide and there is no need to ever silence them, it is dangerous to continue using it.