System Types and Configurations
Chapter 23 of NFPA 72 covers protected premises fire alarm systems, commonly known as local or building fire alarm systems. These systems operate within the confines of the protected building and are responsible for detecting fire conditions, alerting occupants, and initiating emergency control functions. Systems may be configured as dedicated function systems or as combination systems that integrate fire alarm, security, and building automation functions, provided the fire alarm functions take priority.
Alarm Signal Processing
Chapter 23 defines several methods for processing alarm signals before general occupant notification. Alarm verification is an automatic feature that resets a detector input and then waits for a subsequent alarm signal within a defined time window to confirm a genuine alarm. Positive alarm sequence allows trained personnel up to 180 seconds to investigate an alarm condition at the detector location before general notification is activated. Both features have strict conditions and limitations: positive alarm sequence requires acknowledgment within 15 seconds or the system must immediately enter alarm mode.
Annunciation Requirements
Fire alarm systems must provide clear annunciation of system status, including alarm, supervisory, and trouble conditions. Annunciation must be provided at locations approved by the AHJ, typically at the main fire alarm control unit and at remote annunciator locations such as building entrances used by the fire department. Graphic annunciators and text-based displays may be used to provide floor-level or zone-level information.
Fire Command Centers
In buildings where a fire command center is required, the fire alarm system must provide comprehensive system status information at that location. The fire command center serves as the central point for fire department operations and must include the fire alarm control unit, emergency communications controls, elevator status indicators, and other building system interfaces. All system annunciation and control functions required for emergency operations must be accessible from this location.
