The main sources of water vapor and carbon dioxide in a manned space vehicle cabin are the occupants in the cabin. For design purposes, the moisture genera¬tion rate is almost to be considered always greater than the carbon dioxide pro¬duction rate. The steady-state, latent heat load and carbon dioxide production of the occupants are shown to be directly related under conditions of constant cabin temperature and respiratory quotient. Since the allowable concentration levels for carbon dioxide and water vapor on a weight percentage basis are approximately the same, the buildup of humidity occurs more rapidly than carbon dioxide; therefore, by modulating the cabin atmosphere flow to control humidity, the carbon dioxide level is also properly controlled.
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