What synthetic materials are commonly used to make structural firefighting hoods?

The correct choice highlights Nomex and PBI as common synthetic materials used to create structural firefighting hoods due to their exceptional fire-resistant properties. Nomex is well-known for its ability to withstand high temperatures and is inherently flame-resistant. It does not melt or drip when exposed to flames, which greatly reduces the risk of burns to firefighters.

PBI, on the other hand, is also flame-resistant and is known for its excellent thermal stability and strength when subjected to extreme heat conditions. When combined, these materials create a protective hood that not only shields firefighters from heat and flames but also provides comfort and durability during firefighting operations.

In contrast, while polyester/cotton blends may offer some degree of heat resistance, they do not provide the same level of protection as Nomex and PBI. Similarly, polypropylene and nylon are not ideally suited for firefighting applications since they can melt when exposed to high temperatures, leading to severe burns. Lastly, materials like acrylic and wool, although used in some protective clothing contexts, lack the necessary flame-resistant qualities required for structural firefighting gear.