In a single pressurized module of a space vehicle the ventilation system served the functions of cooling down the onboard equipment and the crew, and stirring the atmosphere to make sure that it is uniform in temperature and gas mixture ratio. The paper presents the case for the ventilation system in the multi-modular space station being a binding element for the regenerative crew life support systems – both for the atmosphere revitalization systems and for the water supply systems. A system of equations was formulated and analyzed to describe the state of gaseous contaminants and water vapor in the atmosphere of the interconnected pressurized modules of a space station when it houses a crew (who release gaseous contaminants and water vapor), and when ventilation systems and systems for scrubbing of gaseous contaminants and water vapor are in operation. Constraints on the air flow rates for inter-modular and intra-modular ventilation were determined. Analytical relationships were obtained, which make it possible to calculate the concentration of harmful contaminants in the atmosphere of a space station pressurized module in equilibrium and non-equilibrium states, as well as a formula for determining the air flow rate for inter-modular ventilation. It was found that the inter-modular ventilation flow rate is driven by the need to maintain an acceptable gradient of carbon dioxide (СО2) and water vapor concentrations. The flow rates of inter-modular and intra-modular ventilation determine the power consumption of the ventilation system.