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38 Medical Construction & Design | M A RCH /A PR IL 2017 | MCDM AG.COM assembly including deck, insulation and roofi ng system. > Floor/Ceiling Assemblies – Include the ceiling system, lighting, HVAC outlets and other penetrants through the ceiling, the plenum, structural system, concrete slab, subfl oor and fi nish fl oor. While the tests to determine FSI and SDI ratings only test an individual product, such as a ceiling panel, tests to determine fi re-resistance ratings go a step farther because they are a true system test that includes all the materials and compo- nents used in a roof/ceiling and fl oor/ceil- ing assembly. Failure of any component in the assembly can result in fi re-resistance test failure because it is tested as a total system. Fire-resistance tests measure the length of time an assembly contains a fi re and is able to slow the temperature rise of building elements in the space above the ceiling so as to not ignite combustible ma- terial on the unexposed side of the assem- bly. The resultant fi re-resistance-rated assembly and its time rating are then published in the UL Fire Resistance Directory. The UL Directory provides criteria for the specifi c products installed in each component of the assembly, and also de- fi nes the specifi c manufacturer, type, size and thickness of ceiling panel and suspen- sion system that must be used, as well as all other assembly elements. Any devia- tion results in a violation of the assembly's design, which then results in a loss of its fi re-resistance rating. Fire-resistance assembly requirements Only acoustical ceiling panels specifi cally designed and tested as part of a fi re- resistance-rated assembly can be used in a fi re-resistance-rated fl oor/ceiling or roof/ ceiling assembly. They are always identi- fi ed as such. Most are marked on the back of the panel to make identifi cation easier. Similarly, only suspension systems specifi ed in the UL designs can be used. These systems help maintain the structur- al integrity of the ceiling, and are usually identifi ed by the presence of expansion relief notches in the main runners. If the notches were not there, the grid would expand and distort as it becomes hotter, eventually allowing the ceiling panel to drop into the space below. Another key component of a fi re- resistance-rated assembly is the weight of the ceiling panel. Fire-rated panels must weigh a minimum of one pound per square foot. This will off set the eff ect of hot fi re gases, which can lift a lighter weight ceiling panel and push it out of place, resulting in lost protection. In building codes and UL-listed system de- signs, if panels weigh less than one pound, hold-down clips are required. Smoke partition considerations A type of construction often found in hos- pitals is a smoke partition. Unlike smoke barriers, which are designed to com- pletely stop the movement of smoke from one space to another, smoke partitions are designed to limit the passage of smoke, but not stop it completely. Suspended ceilings used in smoke partitions are not required to have a fi re- resistive rating. However, the panels must weigh at least one pound per square foot. If they are fi re resistive, they automati- cally meet the weight requirement. If not, verifi cation of weight is needed. 1 2 1. Acoustical ceilings help control the growth of a fi re by providing a separation between an occupied space and the potentially combustible materials in the space above the ceiling. 2. Fire-resistive suspension systems have expansion relief notches such as this in their main runners to help maintain the structural integrity of an acoustical ceiling during a fi re. 3. Fire-rated acoustical ceiling panels, like the ones shown in this patient room, must weigh a minimum of one pound per square foot to offset the effect of hot fi re gases, which can lift a lighter weight panel out of place, resulting in lost protection.