When someone in an apartment is airing out the smoke-filled apartment, the smoke detectors in the common hallways sense the smoke, and then sound the alarm.
Almost always, during the time the alarm is sounding throughout the building, the firefighting zone will be identified on the fire alarm panel. Sometimes, the exact smoke detector that sensed the smoke will also be identified on the panel.
Often, the fire alarm control panel, or a remote readout of the control panel (called an annunciator) is in the front entry of the building. As you or other residents evacuate the building, this readout can show the firefighting zone where the fire is located, and sometimes the exact smoke detector that's in alarm.
In order to know where they should go, the firefighters, as they enter the building, read this display.
Then again, all smoke detectors in alarm have also turned on a red light. Even if the annunciator doesn't show the exact smoke detector that's in alarm, when the firefighters arrive in the firefighting zone, they can look up and see which smoke detector has turned on its red light.
As they leave, the firefighters can tell you, or someone there, which smoke detector sensed smoke.
Sometimes, smoke detectors will normally flash their red lights. If the detector normally flashes its red light, the detector-in-alarm's red light stays on constantly.
Sometimes, smoke detectors normally don't normally flash their red lights at all. If the detector doesn't normally flash its red light, the detector-in-alarm's red light might flash, or stay on constantly.
Just look for the red light on a smoke detector that's different from the light on any other smoke detector.
The best time to see exactly which smoke detector has sensed smoke is when the fire alarm system is still sounding the alarm.
Silencing the Alarm
When the fire alarm system is silenced (but not reset), it turns off the horns and strobes in the building. The fire alarm system, though, is still showing that it's in alarm. Any smoke detector that has sensed smoke is also still in alarm.
Because the smoke detector in alarm still has its red light turned on, a good time to see exactly which smoke detector has sensed smoke is when the fire alarm system is still in alarm.
Resetting the Fire Alarm System
When the reset button on the fire alarm system is pressed, the fire alarm panel is reset. In order to reset the panel, though, all the smoke detectors in the building also are also reset. Resetting the smoke detectors means their red lights, showing that they had been in alarm, turn off.
Some fire panels collect a history of what happened. If that's the case with your fire alarm panel, at least the zone where the smoke was sensed will be shown. In their history, some panels can go so far as to show exactly which smoke detector sensed smoke, and even which smoke detector was the first to sense smoke.
If the fire alarm panel has a history, your fire alarm service company can help you find out what happened by retrieving the history. Possibly, they can show you how to retrieve the history yourself.
Then again, there are some panels that don't collect a history of what happened. If that's the case, resetting the panel before knowing which smoke detector sensed smoke means you're out of luck.
In other words, make sure that whoever resets the fire alarm control panel knows which smoke detector senses smoke - before resetting the panel.
Does It Help to Know Which Hallway Detector?
Unless the smoke detectors inside the apartment units are connected to the fire alarm system, knowing which common hallway smoke detector went into alarm will only show a group of near-to-the-detector-in-alarm apartments. More specific information has to be obtained other ways, possibly by witnesses who chanced seeing the airing out of the apartment.
Douglas Krantz
