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September 1, 2006 Paper Detector Spacing on Level Ceilings with Beams and Joists Detector Spacing on Level Ceilings with Beams and Joists Overview 72, The National Fire Alarm Code, recommends using 900 square feet (30 feet center) as a guideline for spacing spot type smoke detectors on smooth ceilings. this is only a recommendation, virtually all manufacturers of smoke detectors this guideline. There has always been a question of how detector spacing to change when the ceiling is not smooth, but is interrupted by beams or The language in the 2002 edition of NFPA 72 code was based on the fi re research reported in 1993-1994 and was considered the best available at that time. However, recent advances in computational uid dynamics (CFD) allowed fi re protection engineers to revisit the current guidelines and make recommendations for changes in NFPA 72. Challenges 2002 edition of NFPA 72 requires that when beams project more than 12 inches the ceiling and when ceiling heights exceed 12 feet, each bay (beam pocket) by the beams should/must be treated as a separate area. That is, each bay would one or more detectors depending upon its physical size. When this requirement fi rst incorporated into the code, it was backed by the best CFD data available at time. Subsequent to this code change, many fi re alarm system designers discovered following the literal code text could mean using a large number of detectors and exorbitant installation costs in many common building designs. Historically, part of the code has been a subject of contention in the fi re protection industry among NFPA 72 Initiating Devices Committee members. Recommendations for Smoke Detector Spacing: 72 requires different detector spacing depending upon whether the structural ornamental members on the ceiling fall into the defi nition of a beam or a joist the depth of those members. The code defi nes solid joist construction as that are greater than 4 inches in depth and spaced 3 feet or less apart. construction, on the other hand, is defi ned as members that are greater than inches in depth that are spaced more than 3 feet apart. For the purposes of spot- smoke detectors, the spacing rules are the same for ceilings with beams and joist construction. level ceilings, NFPA 72 currently requires spacing smoke detectors at one half listed spacing, perpendicular to the run of the beams on a ceiling less than or to 12 feet in height, when the beams are less than or equal to 12 inches deep. parallel to the beams, NFPA requires standard spacing for smoke detectors. this case, the detectors may be mounted on the ceiling or on the bottom of the If the beams exceed 12 inches in depth or the ceiling height of the space 12 feet, the detectors are required in every beam pocket on the ceiling. April 2005, the Fire Protection Research Foundation funded new research using computer modeling to reexamine smoke detector spacing on ceilings with beams joists. The CFD analysis was performed by Schirmer Engineering Corporation NFPA 72 2002 could result higher installation costs. with beams joists affect detector Sensor. Advanced Ideas. Advanced Solutions. Detector Spacing on Level Ceilings with Beams and Joists Vision Systems Ltd. using Fire Dynamics Simulator and Smokeview Version (developed by the National Institute of Science and Technology). The results of research were published in a report entitled, Detector Performance Level Ceilings with Deep Beams and Deep Beam Pocket Confi gurations. The was issued March 28, 2006 and was the basis for recommended changes to 72. on a variety of modeled aming re scenarios, the results of this indicate: NFPA 72 2002 edition requirement for placing smoke detectors every beam pocket when ceilings are greater than 12 feet in height beams are greater than 12 inches in depth is not supported by new study. smooth ceiling 30-foot spacing guideline of NFPA 72, with permitted for narrow space geometry, allows smoke detectors to extend approximately 41 feet on-center and along a corridor. For ceilings up to feet in height, the deep-beam confi gurations do not negatively affect performance. This means that for corridor conditions, spot detectors can be effectively used with deep beams at spacing
September 1, 2006 Paper Detector Spacing on Level Ceilings with Beams and Joists Detector Spacing on Level Ceilings with Beams and Joists Overview 72, The National Fire Alarm Code, recommends using 900 square feet (30 feet center) as a guideline for spacing spot type smoke detectors on smooth ceilings. this is only a recommendation, virtually all manufacturers of smoke detectors this guideline. There has always been a question of how detector spacing to change when the ceiling is not smooth, but is interrupted by beams or The language in the 2002 edition of NFPA 72 code was based on the fi re research reported in 1993-1994 and was considered the best available at that time. However, recent advances in computational uid dynamics (CFD) allowed fi re protection engineers to revisit the current guidelines and make recommendations for changes in NFPA 72. Challenges 2002 edition of NFPA 72 requires that when beams project more than 12 inches the ceiling and when ceiling heights exceed 12 feet, each bay (beam pocket) by the beams should/must be treated as a separate area. That is, each bay would one or more detectors depending upon its physical size. When this requirement fi rst incorporated into the code, it was backed by the best CFD data available at time. Subsequent to this code change, many fi re alarm system designers discovered following the literal code text could mean using a large number of detectors and exorbitant installation costs in many common building designs. Historically, part of the code has been a subject of contention in the fi re protection industry among NFPA 72 Initiating Devices Committee members. Recommendations for Smoke Detector Spacing: 72 requires different detector spacing depending upon whether the structural ornamental members on the ceiling fall into the defi nition of a beam or a joist the depth of those members. The code defi nes solid joist construction as that are greater than 4 inches in depth and spaced 3 feet or less apart. construction, on the other hand, is defi ned as members that are greater than inches in depth that are spaced more than 3 feet apart. For the purposes of spot- smoke detectors, the spacing rules are the same for ceilings with beams and joist construction. level ceilings, NFPA 72 currently requires spacing smoke detectors at one half listed spacing, perpendicular to the run of the beams on a ceiling less than or to 12 feet in height, when the beams are less than or equal to 12 inches deep. parallel to the beams, NFPA requires standard spacing for smoke detectors. this case, the detectors may be mounted on the ceiling or on the bottom of the If the beams exceed 12 inches in depth or the ceiling height of the space 12 feet, the detectors are required in every beam pocket on the ceiling. April 2005, the Fire Protection Research Foundation funded new research using computer modeling to reexamine smoke detector spacing on ceilings with beams joists. The CFD analysis was performed by Schirmer Engineering Corporation NFPA 72 2002 could result higher installation costs. with beams joists affect detector Sensor. Advanced Ideas. Advanced Solutions. Detector Spacing on Level Ceilings with Beams and Joists Vision Systems Ltd. using Fire Dynamics Simulator and Smokeview Version (developed by the National Institute of Science and Technology). The results of research were published in a report entitled, Detector Performance Level Ceilings with Deep Beams and Deep Beam Pocket Confi gurations. The was issued March 28, 2006 and was the basis for recommended changes to 72. on a variety of modeled aming re scenarios, the results of this indicate: NFPA 72 2002 edition requirement for placing smoke detectors every beam pocket when ceilings are greater than 12 feet in height beams are greater than 12 inches in depth is not supported by new study. smooth ceiling 30-foot spacing guideline of NFPA 72, with permitted for narrow space geometry, allows smoke detectors to extend approximately 41 feet on-center and along a corridor. For ceilings up to feet in height, the deep-beam confi gurations do not negatively affect performance. This means that for corridor conditions, spot detectors can be effectively used with deep beams at spacing