Why does my smoke alarm keep bleeping?

This indicates a flat battery, you need to replace the 9-volt battery. To do this you need to take the smoke alarm down off of the ceiling, it will slide away from the base. Replace the battery and re-fit it to the ceiling. If it continues to beep, you will need to get an electrician to replace the smoke detector. Some old smoke detectors do not have batteries, you will need to get an electrician to replace the smoke detector.