Extreme environment clothing
|This article does not cite any references or sources. (June 2007)|
Extreme environment clothing normally refers to clothing for Arctic or mountainous areas on land, although it is sometimes used for survival suits worn by mariners. The basic approach is to insulate one's body from heat loss, and keep liquid water or ice out of the insulation.
The usual clothing for Arctic or mountain regions is a parka and heavy insulated mittens with long gauntlets to protect the wrist, gaiters to keep snow and moisture out of the top of the boots, and wool-felt or down-insulated booties. In high wind-chills, these garments may be supplemented by a mask, usually of oiled wool. In Arctic areas, the typical modern insulation is very fine hydrophobic polyester fiber batting sewn in laps between a nylon shell. The sewing must not compress or quilt the insulation, because the heat leaks out through the thin spots. Most designers now include a moisture barrier on the inner side to prevent condensation from a body's moisture from condensing and freezing in the insulation. Sometimes the moisture barrier has several layers of aluminized plastic film to reflect infrared back to the body. If plastic film is near the skin, usually some lightweight absorbent cloth is between the skin and the film, for comfort.
The feet of booties are usually insulated by a thick layer of flexible closed-cell plastic foam, covered with a boot sole. Traditional tribal insulations are mouth-chewed oiled furs from the winter-killed Arctic animals, with the fur turned toward the body, or in heavy garments, with two layers, the inner turned away from the body, and the outer turned toward the body. The outer layers of skin breaks the wind, and the inner reduces condensation in the fur. Even in modern garments, certain furs (notably Wolverine) are prized for a hood lining, because they do not collect ice crystals from one's breath.
For use in wet areas, the insulation is reduced (because the temperature is above freezing), and a barrier that passes water vapor, but not liquid water is sewn into the outer shell. This barrier passes gaseous water from one's body, yet prevents precipitation from soaking the insulation. The most effective modern fluid barrier is trade-named Gore-Tex, and consists of an expanded felt or mesh of polytetrafluoroethylene (trade name Teflon). The basic principle is that the plastic felt does not wet, and the pores are small enough so water's surface tension will resist high wind pressures. At the same time, the pores are large enough to easily pass water vapor. Gore-Tex is mechanically fragile, and is usually bonded to a polyester fabric, and sewn inside a nylon outer shell. Despite its advantages, even Gore-Tex fabric can be clogged up during sub-zero temperatures if the perspiration freezes.
Another option is to use heated clothing, which contains battery-powered electrical heating elements or gel packs.
Marine survival suits are worn by ship crews operating in arctic and near-arctic waters, and by other people working near water, such as oil rig workers or dock workers. Survival suits provide insulation, floatation, and water protection, so that a person will be able to survive for a longer period if they fall into the water or if their boat capsizes. They are typically brightly coloured, in blaze orange or fluorescent yellow, so that the person will be easier to spot by rescuers. Survival suits come in two different types, wet and dry. Dry suits are very similar to Arctic clothing, except with a waterproof shell, and closed-cell flexible plastic foam for insulation and flotation. Some have vents that allow air and perspiration to pass out without letting water in. Wet suits use foam rubber insulation; the water in the foam warms, and they remain warm event when water gets inside. However, they cannot handle the most extreme cold, and are uncomfortable for extended wear.