The objectives of this research are to exploit the diverse physical properties of Helium, Neon, Hydrogen, Argon and Nitrogen in transient counterequilibration experiments to reveal the relative importance of diffusion, perfusion, decompression ratio, decompression gradient, and the distribution of pre-formed gas nuclei in the processes leading to bubble formation. Current theories now in use predict that counterequilibration of these exotic gases against one another, that is elimination of one during uptake or another will lead to certain degrees of over- or under-saturation; however, both the degree of supersaturation or undersaturation (that is, the predicted decompression benefit) and the numbers of bubbles produced by a given gas switch differs according to the model used. A current paradox is that although perfusion limited models have been shown to hold reasonably well, the maximum supersaturations computed, and the differential exchange rates of helium and nitrogen suggest that diffusion limitation affects the relative kinetics of these two gases. Further, recent studies indicate the origin of bubbles as being primarily dependent upon numbers and size distribution of preformed microgas nuclei. By actually performing these exotic gas switches under isobaric conditions, it will be possible to judge the relative importance of diffusivity (D), solubility (a), total tissue to alveolar gas gradient (delta P) or supersaturation (Pt/P), as well as reveal the probable distributions of "consumable" versus stable, stationary bubble kinetics and bubble formation, leading to more realistic designing of ascent criteria and improved understanding of the etiology of decompression sickness in man.