A First Alert-brand smoke detector provides advanced warning against the dangers of smoke inhalation or a potential fire by sounding an alarm to alert the residents of a home. The model 9120B smoke detector is as vulnerable to false alarms causing its horn to sound as any other smoke detector. You can silence the alarm if it's sounding off needlessly without deactivating or damaging the smoke detector.
Place a ladder against the wall where the First Alert 9120B model smoke detector is mounted. If the detector is mounted to the ceiling, place the ladder beneath the detector instead. Press and hold the "Test/Silence" button on the side of the detector for 10 seconds. Release the button to enter "Silence mode" which quits the alarm from sounding.
Go to the fuse box. Remove the fuse or trip the circuit breaker that connects the electric line to the electrical junction box that that is wired to the 9120B model smoke detector. The detector will now cease to make any noise. Place the fuse back in or trip the circuit breaker again to restore power.
Blow bursts of compressed air against the vents on the side of the smoke detector. The moving air will provide the detector's sensor with the programmed type of response that indicates there is no smoke present. The alarm will go silent.