A modular data center (MDC) includes a volumetric container comprising an enclosure having first and second exterior walls at a forward and an aft end, connected by lateral exterior walls. Information technology component(s) are positioned longitudinally within the container between a cold aisle and a hot aisle. An air handling system includes two or more air handling units (AHUs) each having a return air inlet and a supply air outlet. A supply air plenum directs cooling air flow from the supply air outlets to a supply air opening positioned adjacent to the cold aisle. Backflow prevention mechanisms are positioned respectively at each supply air outlet of the AHUs. Each backflow prevention mechanism is moveable into an open position to allow cooling air flow out of the supply air outlet of a corresponding AHU and a closed position in response to deactivation of an air mover of the corresponding AHU.