Smoke Detector Arrangement in Suspended (Double) Ceilings: A Numerical Investigation Based on International Fire Protection Standards

The performance of automatic smoke detection systems depends strongly on the appropriate placement of smoke detectors, particularly in compartments with suspended (double) ceilings, where smoke movement is affected by ceiling geometry. This study presents a numerical investigation of smoke detector arrangements based on the requirements of five international fire protection standards using the Fire Dynamics Simulator (FDS). The 180 simulations examined four fire growth rates (slow, medium, fast, and ultra-fast), five suspended-ceiling heights, three suspended-ceiling areas, and three burner locations. The results showed that fire growth rate was the dominant factor affecting detector activation time, while suspended-ceiling height, ceiling area, and burner location substantially influenced smoke transport and detector response. Increasing the distance between the suspended and main ceilings generally reduced activation times, whereas reducing suspended-ceiling area from 0.9P to 0.5P shortened mean activation time by 15.12%. With 83.3% overall detector-level activation coverage, the results demonstrate substantial differences in detector response between detectors installed at the suspended-ceiling and main-ceiling levels and provide engineering insight into smoke detector arrangements in spaces with suspended ceilings.