Question of the Day ???

My friend recently asked me this question
"Observation: while going on train or for that matter a bus or a car, if I sit on a window or stand at a door, I always feel air rushing in. I hope u all feel the same. If not, please ignore the rest of the mail.
Question: if so much of air is entering the system from all possible openings, how is it going out? otherwise we may someday see a phenomen of train burst, if we dont find an answer."

Please let me know if anybody knows the answer and I will pass it on to my Curious friend.
He is planning to collect Question of the week. If he does and if its intersting I will pu it up here.