This study aims to evaluate the effects duct leakage had on a stairwell pressurization system in a high-rise residential building by using a network model, CONTAM. The network model was used to determine if the pressurized system was capable of being balanced and perform as intended during a fire incident. The subject building had two stairwells, each fed by a fan located on the 2nd and 29th floors of a 31-story building. Each fan fed a multi-injection duct system which ran through a mechanical shaft located next to each stairwell. This study evaluated the effects that building leakages and temperatures (stack effect) had on air leakage out of the duct system by comparing fan capacities to stairwell pressurization requirement. CONTAM was used to simulate these effects by running both a duct balance method and steady state method. The results from this study determined that as duct leakage rates increased, fan capacities increased to meet the stairwell pressurization requirements for a high-rise building. Additionally, the results determined that the building leakage and exterior temperatures increased the air flow leaking out of the duct system.