Edit: See my third post in this thread for the near-vacuum setup of this airlock, which is impervious to almost any realistically achievable high or low pressure, and is also very good at thermal insulation.   Hi all, Sorry if this has been mentioned before - I haven't seen it anywhere and a brief forum search didn't turn anything up either. I came up with a passive airlock design that keeps different gases perfectly separated without any power use or (to my knowledge) gas de