Underwriters Laboratories, Inc. (UL)
I. UL 181, Standard for Safety, Factory-Made Air Ducts and Air Connectors
This Standard specifies requirements for materials used in the manufacture of factory-made air ducts and air connector systems for use in accordance with NFPA Standards 90A and 90B and the ICC International Mechanical Code. Fibrous glass duct products and systems are classified as Class 1, having a flame spread index not exceeding 25 without evidence of continued progressive combustion and a smoke developed index not exceeding 50. This Standard also establishes a test program applicable to both rigid and flexible fibrous glass duct products and systems as shown in the table below.
(b) Test applicable for flexible air ducts and air connectors that incorporate
vapor retarders supported by grommets or other means of field support.
II. UL 181A, Standard for Closure Systems for Use with Rigid Air Ducts (2nd Edition, 1994)
This standard specifies materials and techniques used in making the following listed closures in rigid duct systems:
- Pressure-sensitive aluminum foil tape UL 181A, Part I (P)
- Heat-activated aluminum foil tape UL 181A, Part II (H)
- Glass fiber fabric and mastic UL 181A, Part III (M)
Under the UL 181A listing procedures an individual closure system may be qualified for use on all manufacturers' fibrous glass duct materials which meet the UL 181 requirement. Use of any non-listed closure system voids the UL 181 Class 1 Air Duct Rating.
III. UL 181B, Standard for Closure Systems for Use with Flexible Air Ducts and Connectors (1st Edition, 1995)
This standard specifies materials and techniques used in making closures in flexible duct systems by means of plastic or metal closure straps, tapes, and mastics. Under the UL 181B listing procedures an individual closure system may be qualified for use on all manufacturers' flexible duct products which meet the UL 181 requirement. Use of any non-listed closure system voids the UL 181 Class 1 Air Duct Rating.
IV. UL 723, Tests for Surface Burning Characteristics of Building Materials
As noted, this Standard is considered by most building code officials to be equivalent to the surface burning characteristics tests set forth in ASTM E 84, NFPA 255, and CAN/ULC-S102.