How would you describe the body functions of a person in a uncirculated room with a lot of people? What I can think of is that it must be hot and not a lot of oxygen. This must cause the people inside to become tired and yawn. But would it affect their breathing? I mean they are not exactly gasping for air, but something in between I would imagine. How would you describe it?
Is there a way out? If not then some might feel panicky and start to gasp. Others just might find it stuffy and start to fan magazines or something. All depends on the mentality of the characters and the situation.
I would say that's entirely dependent on your character. If your MC is introverted/claustrophobic, they might be sweating, breathing deeply, looking around nervously for an exit, or possibly trying to stand against a wall or in the corner. If your MC is comfortable around people/crowds, they might just feel a little hot/stuffy. Now, if you're talking about a room literally running out of oxygen, that's a whole different issue...
