Drysuit

A dry suit or drysuit provides the wearer with environmental protection by way of thermal insulation and exclusion of water, and is worn by divers, boaters, water sports enthusiasts, and others who work or play in or near cold or contaminated water. A dry suit normally protects the whole body except the head, hands, and possibly the feet. In hazmat configurations, however, all of these are covered as well.

The main difference between dry suits and wetsuits is that dry suits are designed to prevent water entering. This generally allows better insulation making them more suitable for use in cold water. Dry suits can be uncomfortably hot in warm or hot air, and are typically more expensive and more complex to don. For divers, they add some degree of operational complexity as the suit must be inflated and deflated with changes in depth in order to minimize "squeeze" on descent or uncontrolled rapid ascent due to excessive buoyancy.

Dry suits provide passive thermal protection: They insulate against heat transfer to the environment. When this is insufficient, active warming or cooling may be provided, usually by a hot-water suit, which is a wetsuit with a supply of heated or chilled water from the surface, but it is also possible to provide chemical or electrically powered heating accessories to dry suits.

The essential components include a shell of watertight material, sufficiently flexible to allow the wearer to function adequately, seals where parts of the body pass through the suit while in use, and a method of sealing the access opening while the suit is worn. Insulation may be provided in part by the suit shell, but is usually largely provided by thermal insulation clothing worn under the suit, which relies to a large extent on trapped air for its insulating properties. An inflation valve with gas supply and dump valve are generally provided, but were not standard on early models.

The main part of the dry suit is a waterproof shell made from a membrane type material, foamed neoprene or a hybrid of both.

Membrane dry suits are made from thin materials which have little thermal insulation. They are commonly made of fabric coated with vulcanized rubber, laminated layers of nylon and butyl rubber known as Trilaminate or Cordura proofed with an inner layer of polyurethane. With the exception of the rubber-coated stockinette, membrane dry suits typically do not stretch, so they need to be made slightly oversized and baggy to allow flexibility at the joints through the wearer's range of motion and to allow the hands and feet to pass trough without difficulty. This makes membrane dry suits easy to put on and take off, provides a good range of motion for the wearer when correctly sized and sufficiently inflated, and makes them relatively comfortable to wear for long periods out of the water compared to a wetsuit or close-fitting neoprene dry suit, as the wearer does not have to pull against rubber elasticity to move or keep joints flexed.

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Wikipedia