Gas dispersion from shallow manure storage pits was experimentally measured and mathematically modeled in a 1:6-scale ventilation chamber. The chamber represents a geometrically scaled model of a production swine grower facility. Gas injection was simulated from shallow pits using carbon dioxide (CO2). The results indicate significant differences in gas concentration between the animal-occupied zone (AOZ) and human-occupied zones (HOZ), especially at ventilation rates representative of mild weather conditions. AOZ CO2 concentrations were 12 times higher than HOZ during minimum ventilation conditions and six times higher during mild weather ventilation conditions. Large variations in normalized CO2 concentration were found as a function of both vertical location from the floor and horizontal location from the inlet, especially at vertical locations representative of the AOZ. Rectangular obstructions, physically representing the overall size of 60 kg pigs, did significantly (p < 0.01) affect gas dispersion at high ventilation rates, but did not significantly (p > 0.05) affect gas dispersion at low ventilation rates, implying that airflow patterns near the AOZ were significantly affected by the presence of rectangular obstructions at high ventilation rates. The mathematical model provided excellent prediction of the measured results. Vertical profiles were closely predicted with large gradients near the floor, in agreement with the measured results.