Duct Silencer has 50% reduction in noise energy which greatly reduces air movement noise levels in your work area or outside the building when located in the duct line on air discharge of fans and dust collectors. Duct Silencer can be installed in new or existing systems. Not to be installed on the inlet side of the dust collector.Air Handling Systems Duct Silencer is constructed of three layers. The inside layer is a wall fabricated of 22 gauge expanded metal.  Standard silencers have a second layer which is a sound-absorbing FireFlex™* Melamine acoustical sculptured wedge foam that withstands constant temperatures up to 320 F.  Another option for the second layer is the **POLYDAMP® Melamine Foam**.  Finally, the outer layer consists of 22 gauge galvanized steel spiral pipe. Please allow 4 to 10 working days for the fabrication of Duct Silencer.*FireFlex™ is the Class 1 alternative to traditional acoustical foams. These materials are constructed of lightweight, porous acoustic melamine. The internal structure is a cellular complex of slim, flexible webs, which are completely open-celled.   FireFlex™ products are uniquely suited for environments where temperatures are high or sparks may fly. It withstands constant temperatures up to 320 degrees F, and meets all Class 1 regulations for flame spread, smoke density, and fuel contribution.**POLYDAMP® Melamine Foam (PMF) is an extremely lightweight material that exhibits exceptional resistance to heat, low flame propagation and smoke.  This product is has a black urethane (BU) facing. Thickness: 2.5 mils. Polyurethane film is a tough abrasion resistant film surface that resists punctures and tears. Polyurethane film also exhibits good resistance to chemicals and moisture.Dia. Length Width05"----36"----09" 06"----36"----10" 08"----36"----12" 10"----36"----14" 12"----36"----16" 14"----48"----18"* 16"----48"----20"* 18"----48"----22"**Must ship by LTL (common carrier)