How do astronauts maintain oxygen levels inside a spaceship?

Spaceships are equipped with advanced life-support systems that manage oxygen, carbon dioxide, and humidity. Oxygen is supplied through onboard tanks or generated by splitting water into hydrogen and oxygen via electrolysis. The oxygen circulates through the cabin, and carbon dioxide is removed using chemical scrubbers like lithium hydroxide canisters. Sensors constantly monitor air composition to maintain a breathable atmosphere similar to Earth’s—roughly 21% oxygen and 78% nitrogen. Backup systems provide emergency oxygen if primary systems fail. Humidity and temperature are also controlled to prevent condensation and mold, ensuring a stable and safe environment for astronauts throughout the mission.