Understanding
the UL Fire Resistance Directories
Loose Fill Material:á As an alternate to Item 3, any loose fill material bearing the UL
Classification Marking as to Surface Burning Characteristics, having a min
density of 0.5 pcf and installed atá a
max thickness of 3-1/2 in.
Ceiling Damper: Maximum
nominal area, 324 sq in. Maximum square size, 18 in. by 18 in. Rectangular
sizes not to
exceed 324 sq in. with a maximum width of 18 in. Maximum damper height is 14
in. Installed in accordance with the manufacturers installation instructions
provided with the damper. Maximum
damper openings not to exceed 324 sq in. per 100 sq ft of ceiling area.
Air Duct:
Any UL Class 0 or
Class 1 flexible air duct
installed in accordance with the instructions provided by the damper
manufacturer.
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