White Paper Clarifies NFPA 72 Smoke-Detector Spacing on Level Ceilings with Beams and/or Joists

Oct. 24, 2006
System Sensor addresses concerns with recent research

St. Charles, IL-based System Sensor, a Honeywell company, now offers a white paper that addresses concerns about correct spacing of smoke detectors on level ceilings with beams and/or joists. System Sensor's white paper cites recent research using computational fluid dynamics (CFD) computer modeling to re-examine smoke-detector spacing on ceilings with beams and/or joists.

The results of the study and accompanying code changes are expected to reduce the overall cost of fire protection systems in beam ceiling applications without compromising occupant safety.

Based on a variety of modeled flaming-fire scenarios, the results of this study indicate that:

  • Recent analysis does not support the 2002 NFPA 72 spacing requirement for placing smoke detectors in every beam pocket when ceilings are greater than 12 feet in height and/or beams are greater than 12 inches in depth.
  • Spot smoke detectors may be placed on the bottom of the beams or in the beam pocket without any significant difference in performance.
  • The concern about mounting smoke detectors a minimum of 12 inches from a ceiling-beam corner, per NFPA 72, is unsubstantiated.
  • The CFD modeling showed no stagnant areas in the beam pockets that would preclude smoke-detector activation.

Based on these findings, the report authors proposed language for addition to the body and annex of NFPA 72. The language clarifies how smoke detectors shall be placed on ceilings with beams and/or joists. These changes are expected to be incorporated into the 2007 edition of NFPA 72, which will be released in late 2006, to quell some of the debate surrounding the current requirements for smoke detectors on beam ceilings.

This information was provided by and reprinted with permission from System Sensor, a global manufacturer of fire detection and notification devices, specializing in smoke detection and notification technology. To download System Sensor’s white paper, visit http://www.systemsensor.com/pdf/detectorspacingWP.pdf.

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