Replace the battery with a fresh one
Make sure the battery is installed correctly
Close the battery compartment fully
Press the test/reset button
Clean dust from the alarm with a vacuum or soft brush
Check whether the alarm is expired and replace it if needed
Reset the alarm by turning off power to it, then restoring power
Replace the entire unit if the beeping continues
If it is a hardwired alarm, check the circuit breaker and wiring connection
Replace all batteries in interconnected alarms if one is low
Contact the manufacturer if the alarm still beeps after troubleshooting