Extreme cold weather clothing

In arctic or mountainous areas, the primary function of extreme cold weather clothing is to trap air as an insulator to prevent heat loss from the wearer's body.

Secondary and necessary is to conduct water vapor away from the body to keep the insulating layers dry.

The U.S. National Weather Service defines extreme cold as −35 °F (−37 °C) with winds less than 5 miles per hour (2.2 m/s).

[1] In these conditions, the unprotected skin of a healthy adult will develop frostbite in ten to twenty minutes.

[citation needed] The original cold weather clothing was made of furs.

The nylon is often bonded to a layer of polytetrafluoroethylene (trade name Teflon) in a form that has holes small enough for moisture to escape, but not allow liquid water to intrude.

[citation needed] Underwear, inner socks, and glove liners are typically thin, soft knits of silk, wool, or synthetic.

A tightly woven fabric prevents wind from disturbing the still air in the insulating layers.

In other work conditions, pacs, or bunny boots, with rubber soles and thick, removable wool felt liners are used.