If it is beeping or alarming, evacuate and check for fire or smoke first
If there is any sign of fire, call emergency services immediately
If it is a hardwired detector, turn off the circuit breaker for that detector
If it has a backup battery, remove the battery after power is off
Twist or slide the detector off its mounting bracket
Press and hold the test or hush button if the alarm is false and the model supports it
Replace the battery if the alarm is chirping due to low battery
Clean dust from the detector with a soft brush or vacuum attachment
Reinstall the detector and restore power when finished
Test the detector after turning it back on
Replace the detector if it still malfunctions