Dry suit

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 from 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 and hazard 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, which requires additional skills for safe use. Dry suits provide passive thermal protection: Undergarments are worn for thermal insulation against heat transfer to the environment and are chosen to suit expected conditions. When this is insufficient, active warming or cooling may be provided by chemical or electrically powered heating accessories. The essential components are the waterproof shell, the seals, and the watertight entry closure. A number of accessories are commonly fitted, particularly to dry suits used for diving, for safety, comfort and convenience of use. Gas inflation and exhaust equipment are generally used for diving applications, primarily for maintaining the thermal insulation of the undergarments, but also for buoyancy control and to prevent squeeze.

Function The dry suit is a form of exposure suit, a garment worn to protect the user from adverse environmental conditions. The two most common purposes are to insulate the wearer against excessive heat loss, and to isolate the wearer from direct contact with a liquid environment during immersion or repeated multi-directional contact with bulk liquids or spray. Most often the liquid is water, usually without significant contaminants, but dry suits also have applications in isolation from hazardous materials and biological contaminants. Most of the insulation function is provided by passive thermal protection in the form of garments worn under the dry suit, The suit itself has the primary function of keeping the insulating garments dry, and allowing them to be maintained at sufficient loft to provide adequate insulation by adding dry gas to the interior of the suit and releasing excess gas. Active heating systems may also be used but are less popular. Isolation of the wearer from contact with the environment for purposes other than thermal insulation usually requires the entire surface of the skin to be kept dry and uncontaminated by the ambient environment. This requires that the seal between the breathing apparatus and the suit is also reliably watertight, which is most effectively provided by sealing the suit to a helmet with redundant series exhaust valves, or a return of exhaled gas to the surface by hose, similar to a gas reclaim system, though there are applications where a lesser level of isolation is acceptable. Dry suits should not leak, but once the suit is sealed, interior humidity rises to 100% and condensation will occur on cold surfaces such as the inside of the suit. A certain amount of dampness is inevitable and common on the inside of the suit after a dive, and is acceptable provided the diver remains warm. Flexing the wrists and large movements of the head may allow water to enter along raised or sunken tendons. This is normal, and to some extent can be avoided or reduced with practice. It can be prevented by attaching the gloves directly to the suit and by sealing the suit to the helmet.

Heat loss

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