Fire suits, which are sometimes known as ‘bunker gear’ and ‘turnout gear’, consist of several protective layers of heat-resistant synthetic materials called aramids. These suits must not only protect the wearer from obvious extreme heat and burns, but they must also allow air transfer (to let cool air into the suit and expel body-heated air away), as well as preventing moisture buildup inside the gear itself. There are three main layers to a fire suit: the outer shell, the moisture barrier and, lastly, the thermal layer.
The silver-coloured outer shell seen in these images here must be tough enough to withstand splashes of molten metal, yet flexible enough to enable the wearer to remain mobile. This layer is often a combination of carefully woven fibres made of a fire-resistant variant of Kevlar called NOMEX. A tight weave ensures that the material resists ripping during often strenuous firefighting activity. It also offers a degree of moisture deflection.
Below the outer shell comes an essential moisture barrier, which prevents liquids and chemicals from passing into the suit. This material consists of a breathable fabric such as Breathe-Tex, sewn in with the NOMEX/Kevlar blend.
Third is a strong thermal layer made from Kevlar-based fibres woven into the material. Flames won’t penetrate through this layer and it also absorbs around three-quarters of a fire’s heat. The temperature of a typical fire ranges from 400-800 degrees Celsius (750-1,470 degrees Fahrenheit).