Proper design of the air ventilation system is critical to maintaining a healthy environment for the ISS crew. In this study, a computational fluid dynamic model was used to model the air circulation in Node 1 to identify the locations where there are low air velocities under nominal operating conditions and several reduced ventilation flow conditions. The reduced ventilation flow conditions analyzed were loss of cabin air fan, loss of inter-module ventilation from Node 1 to the US Lab, and loss of inter-module ventilation from the airlock to Node 1. For nominal operation of the ventilation system, about 5% of the node had air velocity of between 1 and 5 ft/min and 14% of the node had air velocity of between 5 and 10 ft/min. Loss of the cabin air fan and loss of Lab inter-module ventilation did not have a significant impact on the percentage of the node that would have low air circulation. However, the locations where the air was relatively stagnant were shifted depending on the case considered. The failure mode that had the most significant impact was loss of inter-module ventilation from the airlock. This case increased the percentage of the node with air velocity between 1 ft/min and 5 ft/min to 9.5%, and the percentage of the node with air velocity between 5 ft/min and 10 ft/min to 26%.