You said everyone had to leave the room once because of this. So it looks like everyone is aware of this issue and not too ashamed to admit that it exists.
When something like that happens again (e.g. everyone leaves the room or someone mentions bad smell) you could say something to all your colleagues, like: "I know it's an awkward thing to talk about, but please, whoever does that, could you please try to restrain yourself from it? If it's not possible, you might want to visit a doctor."
It might be hard to find out who does that, but it's not that important. Either this person is unwilling to change it because they think it's fun, or they have some health problems and simply can't control it. In any case, there isn't a lot you can do.
Of course, selecting a meeting room with big windows can help as well.