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Following a preceding study of the use of a porous silica membrane system for humidity control in aircraft and space vehicles, the potential weight and volume improvements derived from the use of membranes in the form of thin tubes were investigated. A one-man capacity demonstration model of such a system taking advantage of these considerable savings was developed. Also the wasteful transport of oxygen or air at lower humidities (40-50% RH) can be significantly reduced by impregnating the pores with a desiccant solution. The usefulness of the basic system was extended by using it as a water exchanger in which a dry flushing gas stream provided the driving force across the membrane instead of a vacuum. Porous cellulose containing an aqueous solution of a reversible carbon dioxide absorbent sandwiched between hydrophobic (TFE), microporous membranes showed promise for carbon dioxide removal systems. No advantage over state of the art systems was observed for impregnated microporous silica membranes in this application. A screening program was undertaken to find a substitute for arsenites as catalysts for the absorption and facilitated transport of carbon dioxide. Tin and zinc organometallic complexes with promising properties were identified. For practical application, solubility limitations in particular will have to be overcome. (Author)