THE EFFECT OF STANDARD WAVE CONDITIONS ON DRY SUIT INSULATION WHEN MEASURED ON HUMANS
Testing of immersion suits is commonly conducted in calm or circulatory water. Several investigators have argued that this is an unrealistic test for a suit that is designed to protect a human from hypothermia in open ocean conditions. In support of this argument, Steinman et al. (1) and Romet et al.(2) reported a significant reduction of suit insulation in turbulent water when compared to still water by an average of about 30% when measured on humans. Such differences were found for loose-fitting wet suits but were not investigated for dry suits. Recently, Sowood et al. (3) reported a reduction of dry suit insulation by about 30% in turbulent water (wave height of 60 cm) compared to still water when tested on a thermal manikin.
MEASUREMENT OF IMMERSION SUIT INSULATION : A COMPARISON BETWEEN HUMAN SUBJECTS AND A THERMAE MANIKIN
Thermal manikin. Parallel to the human tests, the immersion suit was also tested using a Thermal Instrumented Manikin (TIM, CORD Group Limited, Dartmouth, Nova Scotia) immersed in the same water conditions and at the same time without interfering with the subject or changing the wave pattern. The probe locations (except for the location of the HFTs that were fixed on the pile garment of the manikin instead of the skin as it was for the humans to avoid applying a large correction factor to the heat flow values; see 2) and the clothing were the same as for the human subjects (see 1 for details). The aluminum skin of the manikin was maintained constant and uniform at 25°C during the tests.
The effect of leakage on the insulation provided by immersion-protection clothing.
The effect of controlled, incremental water leakage on the thermal insulation provided by three immersion-protection assemblies has been measured using a thermal manikin. The results show an average loss of 30% of the initial insulation for a leak of 500 g, 40% for a leak of 1000 g, and nearly 60% for a leak of 3000 g. The assemblies differed only in the thermal insulation layer which consisted of: A. A single thickness of wool (initial immersed insulation 0.63 clo) B. A double thickness of wool (initial immersed insulation 0.79 clo) and C. A layer of polypropylene batting between nylon covers (initial immersed insulation 0.76 clo). Differences between the assemblies in loss of insulation with leakage were small and no evidence was found to support claims that the insulating properties of polypropylene are more resistant to wetting than those of wool. It is considered that the substantial loss of insulation even with small leaks makes it essential that tests of the water-excluding performance of immersion suits are undertaken in realistic conditions rather than in calm water.