EnergyPlus, Method of introducing outside air using "OutdoorAirUnit"

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I am using EnergyPlus and have used OutdoorAirUnit. I want to introduce outdoor air through OutdoorAirUnit to each space without heating or cooling it. I applied OutdoorAirUnit to each floor from the 1st floor to the 4th floor, and saw the results in Output:Variable as Zone outdoorAir unit air mass Flow Rate. However, the results show that mass flow rate is only occurring on the first floor, while the mass flow rate for floors 2 through 4 is calculated as 0. I have configured the nodes and the outdoorair:node separately for each floor, and the settings for floors 2 through 4 are identical to those on the first floor, but I am unsure why the results are showing 0.