How to prevent outside air from flows into the car?

[ELnino]

sometimes when my car was behind lorry or cars with bad exhaust smoke...it will get into my car..i change microfilter..but still can smell it..anyone knows how to prevent this? i use second n third button on the right of this aircond panel..

 

[ELnino]

will try this...hopefully it can solve my problem http://www.bmwclubmalaysia.com/forums/showthread.php?38295-External-smell-getting-into-cabin/page2