CE & UKCA Marked Uninsulated ventilation duct assemblies are intended to be used in environments in which the clearance to combustible supplies and combustible assemblies is at least eighteen inches. ROCKWOOL Curtainrock® is often a stone wool insulation board made for use in ASTM E2307 tested and authorised perimeter fire https://fire-rated-insulation-for23344.snack-blog.com/36831257/the-basic-principles-of-fire-rated-insulation-for-ductworth