Immersion Suit Research Articles

WHOLE-BODY ANTI-EXPOSURE SUITS REDUCE HEAT LOSS DURING ARM EXERCISE AND PROGRESSIVE IMMERSION IN COLD WATER 550

This study evaluated the effectiveness of three whole-body anti-exposure suits (AES) in maintaining body temperatures during arm exercise in cold water(7.5°C). Male subjects (n = 14) were monitored for rectal (Tre), chest (Tch), arm (Tar), thigh (Tth), calf(Tca), index finger (Tfi), and big toe (Tto) temperatures during randomly ordered trials of fire resistant coverall (CON), Marine Corps immersion suit (MARCOR), Naval Clothing and Textile suit (NAVCLO), and MultiFabs Survival suit (MULFAB). Coveralls served as undergarment for AES. Water immersion occurred progressively (20 min to knees, 20 min to waist, and up to 40 min to midchest). During each 10 min interval, subjects rested (2 min), performed a pipe patching task (6 min), and held 25 lb over head (2 min). Maximum exposure time was 80 min. Subjects were able to stay significantly longer (p<0.05) in cold water wearing MULFAB (76 min), NAVCLO(80 min), and MARCOR (74 min) compared to CON (47 min). Analysis of covariance(adjusted for preimmersion values) showed no difference in final Tre([horizontal bar over]X = 36.8°C) and Tfi ([horizontal bar over]X = 20.8°C) among AES and CON. AES Tch ([horizontal bar over]Xs = 35.4°C) and Tar ([horizontal bar over]Xs = 34.7°C) were higher (p < 0.05) compared to CON (29.9°C, 27.5°C, respectively). Final Tth for MULFAB (19.4°C) was higher (p < 0.05) than NAVCLO (16.0°C) and MARCOR (15.2°C) which were higher than CON (11.5°C). Final Tca for MULFAB (14.7°C) and NAVCLO(13.6°C) were higher than MARCOR (11.2°C) and CON (10.4°C). Final Tca for MARCOR (17.3°C) was higher than NAVCLO (13.2°C), MULFAB(11.6°C), and CON (12.1°C). Our findings indicate that during arm exercise and progressive immersion in cold water that MULFAB followed by NAVCLO and MARCOR provided the best maintenance of body temperatures.

The effect of water leakage on the results obtained from human and thermal manikin tests of immersion protective clothing.

The effect of both the volume and location of water leakage on the protection provided by an uninsulated immersion suit was investigated using human subjects and, in corresponding experiments, an immersion thermal manikin. Three volumes of "leakage" to the torso (200, 500 and 1000 ml) were examined, as were two conditions in which no leakage was simulated and one condition in which a 500-ml leak to the limbs was simulated. All leakages were introduced in a standardised way before immersion. The measurements of clothing insulation obtained, both from the manikin and the humans, were in general agreement. The human experimentation provided some support for a 200-ml limit to water leakage in tests of immersion suits. Rectal and aural temperatures remained significantly (P < 0.05) higher when a 500-ml leak was applied to the limbs rather than the torso; this was primarily due to greater heat flow through and from the torso (back) during the immersions with torso wetting. The physiological responses and anthropometric characteristics which determine this response are not present in manikins; the implications of this for the application and design of immersion thermal manikins, as well as the protection of those at risk of immersion in cold water, are discussed. It is concluded that using immersion thermal manikins to provide a single overall measure of clothing insulation will not necessarily distinguish between suits which provide quite different levels of protection for humans.

Test of a quick-don wet immersion suit for off-shore use

Tests of “Spacetime” Survival Coverall suits and the associated gloves and boots of the ensemble were carried out on six men. Four men maintained their rectal temperature above 36°C for six hours in a bath of circulating water at 12°C. Two men had to be withdrawn from the bath because they reached a rectal temperature of 35.5°C, the ethical withdrawal criterion, before the six-hour period had elapsed. Linear regression of rectal temperature versus time during the terminal part of the exposure was carried out for all men. One of the subjects who was withdrawn would almost certainly have had a rectal temperature above 34°C at the end of six hours had he remained in the bath. The other subject would have had a rectal temperature classifiable as “incipient death” (30°C). The relatively rapid fall in rectal temperatures in two subjects did not appear to relate directly to body size, but leakage may have been a contributing factor. Comparison with data in the literature indicates that the immersion suit is advantageous, but separate experimentation would have to be carried out to determine quantitatively how valuable it is in extending the survival time of men immersed in cold water in comparison with other suits on the market.

Maximum acceptable inherent buoyancy limit for aircrew/passenger helicopter immersion suit systems

Helicopter crew and passengers flying over cold water wear immersion suits to provide hypothermic protection in case of ditching in cold water. The suits and linings have trapped air in the material to provide the necessary insulation and are thus very buoyant. By paradox, this buoyancy may be too much for a survivor to overcome in escaping from the cabin of a rapidly sinking inverted helicopter. The Canadian General Standard Board requested that research be conducted to investigate what should be the maximum inherent buoyancy in an immersion suit that would not inhibit escape, yet would provide adequate thermal insulation. This experiment reports on 12 subjects who safely escaped with 146N (33 lbf) of added buoyancy from a helicopter underwater escape trainer. It discusses the logic for and recommendation that the inherent buoyancy in a helicopter crew/passenger immersion suit system should not exceed this figure.

Sweat evaporation and thermal comfort wearing helicopter passenger immersion suits.

Two types of helicopter passenger immersion suit constructed from either a vapour permeable or vapour impermeable material were assessed in terms of their wearers' comfort, their vapour transmission and the moisture accumulation in undergarments. Environmental air temperatures of 21°C and 30°C were compared to simulate different helicopter operating temperatures, and the effects of wearing each type of suit. At 21°C the suits' performance were comparable in terms of increase in undergarment weight, sweat loss, percentage sweat evaporated, effect on rectal temperature and increase in mean skin temperature. At the higher temperature the permeable suit performed significantly better. There was less body weight loss, less sweat uptake into the undergarments and a greater amount of sweat being evaporated. Rectal temperatures and thermal comfort, however, were similar. At higher levels of thermal stress there may be an advantage in user acceptance and minimal decrement in reduction in cold water survival time f...

Submarine Escape: Side, Tube, and Top Egress with Alternative Escape Appliances and Team Sizes

Egress capability with the British Mark VII Submarine Escape Immersion Suit (SEIS) and the Steinke Hood was evaluated for one-, two-, and three-man teams from side-, tube-, and top-egress escape trunks. Top egress was considerably more rapid than either tube or side egress; tube egress was superior to side egress. Egress time increased linearly as a function of team size for both escape appliances. For tube and side egress, escape with the Steinke Hood was more rapid than with the SEIS; the SEIS was superior for top egress. Escape position of a subject within a team had no effect on egress time. When compared to side and tube egress, top egress results in a substantial reduction of total bottom time.