Clearances to Combustibles

Factory-Built Grease Duct Systems must comply with UL1978 "Test Standards for Grease Duct" and must be classified to UL2221 "Tests for Fire Resistive Duct Enclosure Assemblies". ASTM E2336 is the only Standard applicable to Flexible Wrap Systems, all manufacturers require two layers of wrap and a band at the overlaps. For more information, visit and watch the video and see actual testing between "Factory Built" and "Flexible Wrap" Grease Duct Systems.