Outer layer of Gentex ‚“Dual Mirror" ‚® ‚® 545 GSM, aluminized fiberglass fabric. 100% of the fabric surface is aluminum to provide high level reflection of radiated heat. Achieves Class 4 in EN radiant heat protection test: Time to 24oC rise in temperature behind fabric is 108s: (Class 4 is the highest class with a threshold of 95s). The fabric has also been subjected to convection and contact heat resistance tests, as well as molten metal splash. Internal layer of neoprene/nylon taffeta of 182 GSM, which acts as a barrier against steam, and an additional thermal barrier of 160 GSM fiberglass with aluminum sheet. The steam barrier allows it to be used in areas where humidity and high temperature steam pose a risk.