Insulation
applied to the surface of ducts, including duct coverings,
linings, tapes, and adhesives, located in buildings shall
have a flame-spread index not to exceed 25 and a smoke-developed
index not to exceed 50, where tested in accordance
with ASTM E84 or UL 723. The specimen
preparation and mounting procedures of ASTM E2231
shall be used. Air duct coverings and linings shall not
flame, glow, smolder, or smoke where tested in accordance
with ASTM C411 at the temperature to which they are
exposed in service. In no case shall the test temperature
be less than 250°F (121 °C). Coverings shall not penetrate
a fire-resistance-rated assembly.