Coffee Break Training: Fire Alarms & Detection: Smoke Detection in Duct Systems: Part 2   [open pdf - 148KB]

"Another important consideration of duct detector installation is the device's location in relation to duct bends or return-air inlets. As air changes direction in a duct, or as it first enters the duct from a room, it tends to have excessive turbulence. In order to ensure a good laminar flow and mix with products of combustion across the detector sensing element, light beam, or sampling tube, the detector should be installed between 6 and 10 'duct diameters' downstream of the duct bend or return-air inlet. Thus, if the detector is installed in an 8-inch (203 mm) diameter duct, it should be located not less than 48 inches (1,220 mm), nor more than 80 inches (2,032 mm), from the duct bend or return-air outlet. For extremely large ducts (greater than 36 inches (914 mm) wide or tall), additional detectors may be required. Students should refer to National Fire Protection Association (NFPA) 72, National Fire Alarm and Signaling Code for guidance on detector placement."

Report Number:
Coffee Break Training - Fire Protection Series No. FP-2012-31
Public Domain
Retrieved From:
United States Fire Administration: http://www.usfa.fema.gov/
Media Type:
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