Contrary to some misunderstandings, natural fibers such as cotton and wool are not flame resistant. In fact, the only advantage that natural fibers exhibit over synthetics such as polyester is that they do not melt into the burn. Do not use natural fibers and expect to get the type of protection afforded by true flame-resistant materials.

Cotton. Cotton work clothing made of materials such as denim and flannel is a better
choice than clothing made from synthetic materials. Cotton does not melt into the skin
when heated; rather, it burns and disintegrates, falling away from the skin. Thick, heavy cotton
material provides a minimal barrier from arc temperatures and ignites quickly. At best,
cotton provides only minimal thermal protection.

Wool. Wool clothing has essentially the same thermal properties as cotton clothing. Note
the following key points:

● Certain OSHA standards allow the use of natural cotton or wool clothing when a worker is exposed to electrical arcing hazards. The standards suggest weights of 11 oz/yd2 or heavier.

● General industrial practice and industry standards have rejected the use of cotton and wool even though they are permitted. The reason for this is that these natural fibers are not flame resistant. They will burn and, while they are not as bad as some synthetic fibers, they can aggravate the degree of injury.

Synthetic Materials. Untreated synthetic clothing materials such as polyester and nylon provide extremely poor thermal protection and should never be used when working in areas where an electric arc may occur. Some synthetic materials actually increase the danger of exposure to an electric arc. Synthetic materials have a tendency to melt into the skin when exposed to high temperatures.

This melting causes three major difficulties.

1. The melted material forms a thermal seal which holds in heat and increases the severity of the burn.
2. Circulation is severely limited or cut off completely under the melted material. This slows healing and retards the flow of normal nutrients and infection-fighting white blood cells and antibodies.
3. The removal of the melted material is extremely painful and may increase the systemic trauma already experienced by the burn victim.

Synthetic-Cotton Blends. Synthetic-cotton blends such as polyester-cotton are used to make clothing that is easier to care for. Although slightly less vulnerable to melting than pure polyester, the blends are still extremely vulnerable to the heat of an electric arc and the subsequent plasma cloud. Such blends provide poor thermal protection and should not be used in areas where the hazard of electric arc exists.

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