should the fans in my case be blowing out or in

hi me and my uncle have been haveing a little argument on if the fans on my case should be blowing out or both i say it should all be blowing out except two fans in front and he say the fans with the filters should be blowing in and the ones with out should be blowing out

 

He is correct. Fans are used to create an airflow inside the case to remove the heat. You want the incoming air to be filtered to reduce the amount of dust entering your case. On my cases, the fans in front bring cooler air in from outside, the ones in back blow out to remove the hot air, creating an airflow.

 

so what about if theres a fan at the top of the case

 

Most tower style cases follow these rules...

Top of the case = Out
Side panel of case = In
Front panel of case = In (some have filters)
Rear panel of case = Out