Close-up of bus duct with 2 layers of Mylar wrappings. These overlap and are held together with Scotch tape. These wrappings are "rated to 130°C", which is fairly useless in a building fire or fire testing as These can go up to 1100°C, where the wrapping catch on fire, which spreads, along with smoke and heat, through the inside of the bis duct, to the unexposed side (in the test lab) or, worse, an unengaged fire compartment.