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.