Ductings are conduits or passages used in heating, ventilation, and air conditioning (HVAC) to deliver and remove air. The needed airflows include, for example, supply air, return air, and exhaust air. Ducts commonly also deliver ventilation air as part of the supply air.Ductwork materials includes rubber, stainless steel, polyurethane, silicone, PVC, neoprene-dipped polyester fabric. The best flexible air filter duct for commercial buildings in extreme climates are made from silicone, PVC, rubber, and stainless steel