A multi-element fixed control volume air interchange system performance computer model was developed and upgraded for the evaluation of atmospheric characteristics inside each habitable volume on the mated Orbiter/Mir-Station. The results from this computer model has been utilized to assess and determine the Orbiter airflow supply capabilities, and to develop mated air interchange system design limitations and requirements. The results from this performance model were also used to predict possible air interchange system operating constraints, such as occupancy limitations in each chamber, during the Orbiter/Mir-Station docking mission. In order to verify the validity of the simulated computer model results, several post Mir missions flight data were obtained and compared. Based on the results of comparison between model results and post flight data, it is concluded that this model can provide an acceptable and reasonable atmosphere prediction and evaluation for assessing all the habitable volumes inside the mated Orbiter/Mir-Station.