Smoke Detector Logic in the Fire Alarm System
Objective
The purpose is to identify fires early on, triggering an alarm and initiating a safety response.
Logical Flow
1). Normal Conditions:
The smoke detector continuously analyzes air quality.
No smoke indicates a normal signal (typically the 24V DC loop is intact).
2). Alarm Condition:
When smoke is detected, the internal sensor activates.
The detector’s status changes (resistance reduces or it becomes short).
The Fire Alarm Control Panel (FACP) gets this signal.
3). FACP Actions:
Verifies the detector signal.
Triggers
Visual alarm (strobes or flashing lights)
Audible Alarm (Hooter, Buzzer, or Siren).
Relay Output (for controlling AHU shutdown, fire damper closure, elevator recall, etc.)
BMS/SCADA integration (if needed)
Location Display
The panel displays the actual detector location/zone in the alarm.
Quickly identifies the source of a fire.
Optional Logics
Pre-Alarm Level: Low smoke levels cause a warning before a complete alarm.
Double Knock: The alarm only sounds when two detectors in the same zone detect smoke (false alarm prevention).
Delay Timer: a period of delay to prevent annoying alarms.
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