The fibrous glass duct system is used to conserve heating and cooling energy and to control duct-borne noise in commercial, institutional, or residential heating, ventilating, and air-conditioning ductwork operating in the range of+2 in. w.g. (+ 500 Pa) static pressure, up to at least 5,000 fpm (25.4 m/sec) internal air velocity, and internal air temperature between 40˚F (4˚C) and 250˚F (121˚C). Ducts are only for indoor use and should be located in areas where ambient temperature does not exceed 150˚F (66˚C).