NFPA 72 code sections · Capstone: Design, Explain & Defend
Sharing a panel with security or HVAC? Fire wins, always
A combination system shares equipment or pathways with non-fire functions — a security panel, a building automation front-end, a paging system. The code allows it, with conditions: fire alarm signals take precedence over all other signals; a failure, short, open or ground in the non-fire portion can't impair any fire alarm function; non-fire equipment that affects the fire alarm must be listed for that use; and the fire alarm operation can't be prevented by the other system's user interface. If the burglar panel locks up and the fire alarm goes with it, the design was never compliant.
NFPA 72 reference
Chapter 23 — Protected Premises Fire Alarm Systems
23.8.4 Combination Systems (23.8.4.1 fire alarm precedence; 23.8.4.2 non-fire faults shall not impair fire alarm functions; 23.8.4.3 equipment listing; 23.8.4.4 shared user interfaces)
References use NFPA 72 2019/2022 numbering — section numbers can shift between editions, so confirm in the edition your AHJ has adopted.
On the job
A campus integrates fire alarm annunciation into the building automation graphics. During a software update the BAS server goes down and the security desk loses the fire alarm display — but the fire alarm control unit, its own annunciator and the central station connection keep running untouched. That separation is what the combination-system rules require; the graphics were a convenience, not the required annunciation.
Quick check
1. In a combination system, when a fire alarm and a security signal occur together:
2. A fault in the non-fire part of a combination system:
3. The required fire alarm annunciation may be replaced by a BAS graphics screen:
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