NFPA 72 Initiating Devices
Heat, Smoke, Duct and Door-Release Detectors, Manual Boxes, Waterflow and Supervisory Devices (Chapter 17)
NFPA 72-2019 National Fire Alarm and Signaling Code (DBPR CIB reference list); read in the NFPA free-access viewer 2026-09-21 · Reviewed 2026-09-21
Chapter 17 does not require detectors — other codes do (NFPA 101, the Florida Building Code). It says where and how far apart they go once required. The exam numbers: 4 in. / 12 in., 0.7 S, 50 % / two-thirds, 36 in., 30 ft, 20 °F, 32–100 °F / 93 % / 300 ft/min, 10 ft / 20 ft / 6 ft / 36 in., 42–48 in. / 5 ft / 200 ft / 40 ft, 90 seconds, two revolutions / one-fifth, 10 psi, 3 in. / 12 in., 40 °F.
1. General rules — 17.4, 17.5
- Guards or covers on initiating devices are listed for use with the device.
- Every initiating device has duplicate terminals or leads so the wiring can be monitored for integrity (no pigtail-splicing two wires under one terminal).
- A detector in a concealed location more than 10 ft above the floor, or whose indicator is not visible to responders, gets a remote indicator with a placard naming the detector and the area protected (not required if the control unit identifies the specific detector).
- Detectors are not recessed unless listed for recessed mounting.
- A partition reaching within 15 % of the ceiling height makes the spaces separate rooms (17.5.2).
- Total (complete) coverage includes all rooms, halls, storage areas, basements, attics, lofts and spaces above suspended ceilings. Exceptions: concealed spaces filled with noncombustible insulation, small concealed spaces over rooms ≤ 50 sq ft, stud/joist spaces < 6 in. apart; below open-grid ceilings with openings ≥ ¼ in., material thickness not exceeding the least opening dimension and openings ≥ 70 % of the ceiling area.
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