25 Insulated Ul 181 Class 1

A GUIDE TO INSULATED HVAC DUCT SYSTEMS

1 Types of insulated air duct systems ... (25.4 m/sec) internal air velocity, and internal air temperature between 40˚F (4˚C) and 250˚F (121˚C). ... products qualify under UL 181 as Class 1 Air Ducts, meeting the fire safety requirements of NFPA 90A and 90B including limited combustibility. They also comply with all

  Class, Insulated, Class 1, Ul 181