The wearing of synthetic athletic clothing containing polyester and nylon next to skin has been prohibited from use by most fire departments. When exposed to extreme heat, flames, or electrical current, clothing containing non FR synthetic materials like polyester will melt and can fuse to the skin. This essentially creates a molten second skin layer which can lead to disfiguring burns, even under turnout gear. Thats why Blauer offers a selection of cotton and cotton-rich base layers, a superior choice for public safety professionals; because they will not melt to the skin.