Unfortunately, no one has followed a balloon up to see what really happens up there as far as I know. And on top of that, you have to keep adding air without tying a knot to over-inflate a balloon ...
As the rubber sheet is pulled down the volume of the jar increases, the pressure therefore decreases and air is drawn in through the glass tube inflating the balloons, which represent the lungs.
“Unlike other adventure sports, hot air ballooning is regulated by ... training which is learning how to set up the balloon, anchoring, inflating, deflating, tracking the balloon after take ...