Electronic Alarms and Home Security Devices - Fire Alarm Keeps Beeping

I have a hard wired fire alarm with a battery back up. It started giving out low intermittent beeps so I figured it must be a low 9v battery. I installed a brand new battery but the alarm continues to beep. I know my house isn't on fire. My son is giving me the grief because he can't sleep because of it. What can be causing this ? HELP !

You could try to hold the 'test' button for a few seconds..might clear any glitch.
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How old is the unit? - More than 8-10 years should probably be replaced anyway.

I agree with the possible age issue here.If it's even 5 years old this may be the problem.The sensors do eventually stop working correctly.

Some models do "chirp" if they have a dirty sensing chamber. You can try giving it a good cleaning with some canned air, but as someone has pointed out, they do have a design lifetime of about 10 years, and since few people keep them cleaned and maintained, the reality is more like 5-7 years.

Cleaning
It is recommended that the detector be removed from its
mounting base to facilitate cleaning. The detector is cleaned
as follows:
NOTE: Before removing the detector, notify the proper
authorities that the smoke detector system is undergoing
maintenance and will be temporarily out of service. Disable
the zone or system undergoing maintenance to prevent unwanted
alarms.
1. Vacuum the screen carefully without removing it
2. Reinstall the detector.
3. Test the detector
4. Notify the proper authorities that the system is back on line.

and have checked to circuit breaker for the smoke detectors it might be beeping do to no ac power