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.