CE & UKCA Marked Uninsulated air flow duct assemblies are meant to be used in environments where the clearance to combustible supplies and combustible assemblies is not less than eighteen inches. ROCKWOOL Curtainrock® is usually a stone wool insulation board created for use in ASTM E2307 tested and permitted perimeter https://fireratedductworth80001.dailyhitblog.com/42263335/the-ultimate-guide-to-fire-rated-insulation-for-ductworth