What is the thickness of a fire-rated duct? A fire-rated duct ought to be built with a single pores and skin, getting a complete thickness not exceeding 2mm. This measurement consists of the intumescent coating, which happens to be essential for maximizing fire resistance. Based on the World Wellbeing Organisation https://fire-rated-ductwork70011.techionblog.com/39725610/fire-rated-insulation-for-ductwork-things-to-know-before-you-buy