Planes don’t recycle air that much. While there is some recirculation, outside is constantly pumped in (either bleed air from the engines, or from electric comp

Planes don’t recycle air that much. While there is some recirculation, outside is constantly pumped in (either bleed air from the engines, or from electric compressors on the 787) and there’s a valve that lets air out at the correct rate to maintain the desired cabin pressure. I can’t remember the exact timing, but think I recall it being something like every 10 minutes or so that all the cabin air is replaced.