Fire Alarm and Life Safety Systems
Fire alarm work is the most heavily regulated low voltage discipline. Candidates must understand the difference between conventional and addressable systems, initiating devices (smoke, heat, duct, waterflow, tamper) and notification appliances (horns, strobes, speakers), and the circuit classes - Class A (redundant path) versus Class B (single path) - and how each affects survivability. Know NFPA 72 concepts: device spacing and coverage, the alarm, supervisory, and trouble signals, annunciation, and the requirement for monitoring. Understand that fire alarm cable must be rated and installed per code (often FPLR/FPLP), separated from power, and that survivability requirements apply in high-rise and assembly occupancies.
Traps: confusing supervisory with alarm signals (a tamper or valve closure is supervisory, not alarm); assuming any low voltage cable is acceptable for fire alarm; forgetting that smoke detector spacing depends on ceiling height and configuration; and mixing up notification appliance candela requirements with audibility. Another common trap is the interface between the fire alarm and other systems - door hold-opens must release, elevators recall, and HVAC shuts down - and the requirement that interfaces be monitored for integrity.
Worked rule of thumb: for any interface, ask "what happens if the wire breaks?" If the answer is "nothing detectable," the circuit needs end-of-line supervision or a monitored module. Also remember that acceptance testing and documentation per NFPA 72 are part of the job, not an optional extra.
Always confirm the locally adopted edition of NFPA 72 and any amendments.