Barometric and static pressure relief dampers should be used on many zoning systems to control static pressure, register noise, and to insure proper CFM across the coils and heat exchangers. Both barometric and static pressure relief dampers usually mount in a duct that is attached from the supply plenum to the return air plenum; excess air is routed back through the unit and additionally heated or cooled. Our products and design techniques are "by-the-book", and conform to typical industry practice and guidelines.