Abstract: An insulating material suitable for use in a diver's garment or garment-like apparatus. The insulating material comprises a multiplicity of layers of a flexible, stretchable material. These layers include a central core consisting of a gas permeable, preferably multicomponent, layer of a material that is substantially non-compressible when at least partially evacuated and subject to hydrostatic pressure when immersed in water. Two further and gas impermeable layers are provided, each of these further two layers being of a stretchable material with the central core being disposed intermediate to said layers. When formed into a diver's garment, the peripheral edges of the insulating material are sealed, and sealable closure means are provided in at least one of the gas impermeable layers to communicate with the central core.

Abstract: A heat receiver is provided comprising a housing through which the breathing mixture passes in one direction and through which the exhaled breath passes in the opposite direction. The housing contains heat conductive elements through which the breathing mixture and exhaled breath pass and spacers positioned one between each pair of adjacent heat conductive elements. The spacers are poor heat conductors and non-hygroscopic to minimize moisture retention. In use, exhaled breath warms the heat conductive elements sequentially so that each element will be slightly cooler than the last element exposed to the exhaled breath. There will be minimal heat stored in the spacers and the moisture content of the exhaled breath tends to be carried through the device so that upon drawing breathing mixture through the device a substantial part of the sensible heat originally in the exhaled breath will be reclaimed by the breathing mixture. The latent heat originally in the exhaled breath will be lost.