It seems to me that with a fire producing a large amount of smoke in a closed container (albeit with a relatively small outflow valve) that no matter how you set up the airflow system, the smoke will eventually (and possibly rapidly) fill up the entire container. Considering the massive amounts of smoke that can come from some fires, it doesn't seem to me that one can eliminate a large amount of smoke unless you have an exit path that is very, very large. Am I wrong here?