Engineering data on the design and operation of algal culture systems for photosynthetic gas exchange are virtually non‐existent. The authors have conducted intermediate and definitive level engineering studies to characterize algal systems—with a view to extrapolating to larger‐scale systems for life support in closed spaces. Light intensity, carbon dioxide concentration, and dilution rate were the principal parameters used to control the photosynthetic rate and, consequently, oxygen production. Carbon dioxide absorption rate, equilibrium density, and cellular growth rate were also investigated. It was found that: (1) properly jacketed high intensity, incandescent lamps provided a suitable light source for growing algae; and (2) physiologically safe (0·5 per cent) concentrations of carbon dioxide produced growth comparable to that obtained at higher concentrations. A dilution rate of nearly 0·1 volume change per hour produced the best oxygen yield (2·41 × 10−3 lb/h) for the definitive system. Maximum cell doubling time was 5·1 h. The highest culture density attained was 5·9 mm3/ml, and the maximum dry weight algae yield was 3·0 × 10−3 lb/h.