ISS is cruising high above us at altitude of mind spinning velocity, the station is designed to maintain life support for its crew. The crew are humans and thus need air to breath, waste to be removed, food, heat, and work to stay psychologically stable. Now the question I have is, the astronauts oxygen is converted to CO2 as they breath out but what happens to nitrogen? I guess the actual question is...how does the station maintain the balance of 78% nitrogen gas and the rest oxygen aboard the station? Is oxygen being released at a continuous rate and that rate increases or decreases according to the human respiration or release of carbon dioxide? Carbon dioxide is removed on ISS cemically by Lithium cells...but when this carbon dioxide is removed is extra oxygen added at a specific rate? :bugeye: Anyone knows?

ISS is cruising high above us at altitude of mind spinning velocity, the station is designed to maintain life support for its crew. The crew are humans and thus need air to breath, waste to be removed, food, heat, and work to stay psychologically stable. Now the question I have is, the astronauts oxygen is converted to CO2 as they breath out but what happens to nitrogen? I guess the actual question is...how does the station maintain the balance of 78% nitrogen gas and the rest oxygen aboard the station? Is oxygen being released at a continuous rate and that rate increases or decreases according to the human respiration or release of carbon dioxide? Carbon dioxide is removed on ISS cemically by Lithium cells...but when this carbon dioxide is removed is extra oxygen added at a specific rate? :bugeye: Anyone knows?
Yes. They have LOX tanks aboard that are resupplied by shuttle trips. It's closely monitored by automatic equipment with O2 sensors and continuously replaced as needed.