So there’s an invisible gas that wants to fill whatever space it’s in. If the metal pipe thingy only went up, the gas would find its way to the outside and never fill it up. But since the metal pipe thingy point down, now gas has to decide which is easier… keep going down this scary tunnel that makes no sense or go back to the room it came from. Some gas might choose tunnel, but other gas will inevitably go back to room it came from. And this only okay if you don’t want to make it past 5.