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.

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.

This effect is prevented or mitigated by almost any dry suit, as the cold water is kept from direct contact with most of the body and the immediate heat loss is reduced considerably.

However, the ability to perform useful work like staying afloat declines substantially after ten minutes as the body protectively cuts off blood flow to "non-essential" muscles.

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.

[7]: 73 Membrane dry suits for surface use may also be made of a waterproof but breathable material like Gore-Tex to enable comfortable wear without excessive humidity and buildup of condensation.

Underwear which is flexible and stretches, particularly at the joints, will allow the diver more freedom of movement, and is less likely to chafe, and for diving use, materials which resist compaction under light pressure will maintain a more even thickness in use, which will provide better insulation for the same overall volume.

The spring-loaded push-button inflation valve is usually mounted over the chest for easy access, and is manually operated by the diver during descent to maintain the loft of the undergarments for insulation and to prevent discomfort from suit squeeze.

Both types of BCD and dry suit low pressure inflator hoses are supplied with a standard fitting for connection to a scuba regulator first stage low-pressure port.

Surface-use dry suits do not normally have exhaust valves, but the wearer may vent excess air by crouching down and hugging the legs while slipping a finger under the neck seal.

[1]: Ch1 During ascent, the diver has several things to monitor and do, so an adjustable automatic exhaust valve which provides hands-free operation helps reduce this task loading.

The BC is used to compensate for mass change due to consumption of breathing gas, while the dry suit is kept at a near constant volume to optimise thermal insulation.

Survival suits will typically be a one-piece design made of fire-retardant neoprene, optimized with quick donning features, and produced in high visibility colours with reflective tape patches.

Any customising of the suit is done after this process, and requires cutting and gluing and taping of additional seams, which are generally not as reliable and strong as the original structure The thickness of the rubber layer can be varied and patches added for abrasion resistance.

[7]: Ch.4 Seals, zippers, boots, pockets, and other accessories, are usually glued on to the shell after assembly, and joins and edges may be reinforced by seam tape in high stress areas or to improve watertightness.

In situations where the air is warm but the water cold, a prolonged time on the deck of a boat donning a dry suit and other gear can present a risk of overheating to the diver.

A side effect of overheating is that the sweat produced by the diver can condense on the inside of the suit, or wet the thermal undergarment, reducing the insulating qualities during the dive.

This can be a limiting factor on the endurance of the surface team if inadequately insulated and sheltered, and can have an impact on the divers on exiting the water in wet exposure suits.

[63]: 117, 126 During descent the air in the suit is compressed and unless more is added, the folds may be pressed together so tightly by water pressure that they pinch the skin, which is painful and may cause local bruising.

Although it is possible to dive like this, the risks are higher than when using a buoyancy compensator for the following reasons:[4]: 11–19 [67] An over-tight neck seal can put pressure on the carotid artery, causing a reflex which slows the heart, resulting in poor oxygen delivery to the brain, light-headedness and eventual unconsciousness.

It is a recommended practice to ensure that the bubble remains small and at the top of the body by using the buoyancy compensator to counteract any excess weighting, keeping only the minimum gas necessary to maintain undergarment loft inside the drysuit.

[41] The recommended procedure in all such inversion incidents, is for the diver to bend at the knees and powerfully swing the arms to do a backward or forward roll to the upright position without delay, to allow the gas to flow to the shoulders and arms, allowing the automatic dump valve to operate, and then vent the suit, if needed, by manually opening the neck seal (sometimes called "burping the suit") by breaking the seal-neck contact with a finger.

[70] Expanding on improvements already made by another engineer, George Edwards, Siebe produced his own design; a helmet clamped to a full-length watertight canvas diving suit.

[72] In France in the 1860s, Benoît Rouquayrol and Auguste Denayrouze developed a single stage demand regulator with a small low pressure reservoir, to make more economical use of surface supplied air pumped by manpower.

To add to this problem, a runaway ascent could cause sufficient internal pressure to burst the seal at the corselet, which could result in a catastrophic loss of buoyancy, and the injured diver sinking back to the bottom in a flooded suit.

At the surface the diver could struggle a short distance using the arms, but underwater would normally walk on the bottom and climb up and down over obstacles, taking care to avoid passing under anything that could foul the air hose.

The diver needed to remain upright when ascending to allow venting of excess air through the helmet exhaust valve, and would either be lowered and pulled up by the tenders, or would slide down the shotline and climb back up it.

This two piece suit was made from thin and elastic rubber, optionally bonded to a knit fabric reinforcement liner except at the sealing areas at the neck, wrists and waist.

The Siebe-Heinke Dip Suit for recreational diving, swimming, yachting and fishing, was a seamless black dipped-latex jacket with neck and cuff seals, and trousers with separate yellow latex cummerbund for the waist-seal.

Overpressure valves were installed in the ankles, wrists and neck of dry suits to remove excessive air introduced through the face mask to prevent discomfort created by squeeze, which also increased the insulation capacity of the undergarments.