Fire Alarm and Life Safety Systems
Fire Alarm and Life Safety Systems tests NFPA 72 installation, initiation, notification, supervision, and testing. Expect questions on addressable devices, Class A and B circuits, battery calculations, detector spacing, visible notification, elevator recall, and documentation.
Core rules
- NFPA 72 governs performance, installation, testing, and maintenance. The FACP must supervise initiating and notification circuits and annunciate trouble and supervisory conditions.
- Class A circuits continue to operate with a single open or ground fault; Class B circuits do not. Know the project specification before selecting a pathway class.
- Battery calculation includes standby load for the required time plus alarm load for the required alarm duration, then applies a derating factor.
- Respect detector spacing and clearance from air diffusers. Visible notification must meet ADA and adopted code requirements. Elevator recall and duct detector functions require coordinated testing.
- Record device addresses, test results, and acceptance documents. Testing is not complete until the AHJ accepts it.
Worked example
A 24 V system has a 0.25 A standby load for 24 hours and a 1.0 A alarm load for 5 minutes. Standby is 0.25 x 24 = 6.0 Ah. Alarm is 1.0 x 5/60 = 0.083 Ah. Total is 6.083 Ah. At 80 percent usable capacity, the required battery is 6.083 / 0.8 = 7.6 Ah, so a 7 Ah battery is too small; an 8 Ah or larger battery is needed.
Traps
Using only the alarm load; forgetting the derating factor; leaving an end-of-line resistor off a supervised circuit; blocking a smoke detector; and testing devices without testing the integrated cause-and-effect matrix.