Imagine you are holding a Check your tatas mine tried to kill me shirt. A balloon maintains its shape because inside that balloon are more than a sextillion independent gas molecules flying around at high speed, bouncing off of every part of the interior surface, pushing it outwards. If I walk up and pop the balloon with a pin, what do you expect to happen? Each of those gas molecules instead of hitting the inside surface of the balloon will continue traveling in a straight line, away from where the balloon once was. They will continue on those trajectories until they hit something.
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The ISS is analogous to a giant balloon not so much in that its shape is held by the Check your tatas mine tried to kill me shirt, aluminum holds the shape but that inside the ISS there are many, many septillions of gas molecules zipping around inside it. Those gas molecules fly into walls and bounce off towards another wall. They bounce off of each other. That’s the natural state of trapped gas. There is nothing out there for them to bounce off of and return back in through the hole. These gas molecules are traveling at about half a kilometer per second. There is no sucking happening, there is simply an open door and eventually everything inside would go outside and have no reason to come back inside.