CE & UKCA Marked Uninsulated ventilation duct assemblies are intended to be used in environments where the clearance to combustible materials and combustible assemblies is at least eighteen inches. ROCKWOOL Curtainrock® is usually a stone wool insulation board created for use in ASTM E2307 tested and authorised perimeter fire containment https://dominicksjyma.techionblog.com/36974860/the-greatest-guide-to-fire-rated-ductworth