The fire alarm system is the central nervous system of a hospital's life-safety posture: it senses fire and smoke, supervises the suppression systems, drives the building into a safe configuration, and tells staff and occupants what to do — all under the assumption that the building is not evacuated but defended in place. This article covers detection, alarm initiation, notification (including emergency communications and mass notification), the fire alarm control unit and its supervised circuits, and the survivability, power, and acceptance-testing requirements that govern the system in U.S. healthcare facilities. Suppression systems themselves (sprinkler/standpipe, clean-agent, kitchen hood) are covered by sibling Articles; this Article owns the part of the system that detects, decides, and communicates, and the interlocks it commands are covered in depth by the sequence-of-operations sibling.

The governing code and why healthcare is different

The fire alarm system is designed, installed, tested, and maintained to NFPA 72, National Fire Alarm and Signaling Code. NFPA 72 is the means; the requirement to have the system, and what it must do, comes from the occupancy chapters of NFPA 101 (Life Safety Code) — specifically the new and existing health care occupancy chapters (18 and 19) — adopted by reference under the CMS Conditions of Participation (42 CFR §482.41), which obligate accredited hospitals to comply with the CMS-adopted edition of NFPA 101 and 99. The International Building Code / International Fire Code (IBC/IFC) apply in parallel where the local Authority Having Jurisdiction (AHJ) adopts them, and NFPA 99 (Health Care Facilities Code) layers in risk-category and emergency-systems requirements. NEC (NFPA 70) Article 760 governs the wiring and circuit classification of fire alarm systems, and Article 517 governs the essential electrical system that backs them up.

What makes healthcare distinct is the defend-in-place strategy. Hospitals are full of non-ambulatory patients — on ventilators, in surgery, in NICUs — who cannot self-evacuate. The fire response is to contain the fire behind rated smoke compartments and relocate affected patients horizontally to an adjacent compartment, not to empty the building. This single fact reshapes the whole alarm design:

• Notification is selective and staff-directed, not a general "everybody out" evacuation tone everywhere.
• Smoke compartmentation drives the detector and door-release layout — the system must close doors and command HVAC to keep the fire compartment isolated.
• Positive alarm sequence (PAS) and staff investigation are common, because a reflexive full alarm in a patient-care environment is itself a hazard.

Detection: initiating devices and where they go

Detection is the input layer. NFPA 72 classifies initiating devices by what they sense and how they report.

Automatic detectors

• Smoke detectors — photoelectric (better for slow, smoldering fires; the workhorse in corridors and patient areas) and ionization (faster for flaming fires). Modern systems use addressable photoelectric or multi-criteria detectors. Spacing follows NFPA 72 listed coverage (a common rule-of-thumb is roughly 30 ft on smooth ceilings, reduced for beams, high ceilings, and airflow).
• Heat detectors — fixed-temperature and rate-of-rise, used where smoke detection would false-alarm (kitchens, mechanical rooms, dusty or humid spaces).
• Duct smoke detectors — installed in air-handling supply/return ducts per NFPA 90A to shut down or reconfigure HVAC and prevent smoke distribution; they are a supervisory/control input in most healthcare designs rather than a general-alarm input, an important distinction discussed below.
• Multi-criteria / multi-sensor detectors — combine smoke, heat, and sometimes CO sensing with software algorithms to cut nuisance alarms, increasingly specified in patient areas.
• Beam and aspirating (air-sampling) detectors — for atriums, large lobbies, and high-value/high-sensitivity spaces (data centers, imaging suites, pharmacy clean rooms).
• Flame detectors — specialized, for specific hazard areas.

Manual initiation

• Manual pull stations at exits and along egress paths per NFPA 101/72 travel-distance limits. In many healthcare designs, activating a pull station drives staff alarm and the protective sequence but, like most signals, is managed within the defend-in-place response.

Suppression-system supervision — the fire alarm system supervises and monitors the suppression systems even though it does not suppress:

• Waterflow switches on sprinkler systems initiate an alarm when water moves.