Which way should computer case fan blow?

I had install 2 80mm fans (side by side) at the side of my case (just beside my graphic card). Should I set them all blow in or out? Or 1 in and 1 out? I need suggestions. Thanks a lot.Which way should computer case fan blow?
They should blow out. If you had them on opposing sides of the case, one blowing in and one blowing out would create a nice flow, but not if they are next to each other.Which way should computer case fan blow?
The general idea is for air to be taken in from the front and blown out from behind. If you have placed your fans behind the case (where all your ports are), the air needs to blowing out.





If you have a vent at the top, you could also place a fan there to blow out the heat.
Both of them should blow out.





Why?





If fans blow in, that will suck in tons of dirt, dust, and debris which could ground or short out your motherboard or other components. While it may not happen immediately, it could slowly lead to your PC frying out over time.





Fans need to blow out, and have adequate air flow to allow it to draw cool air in from another direction, so there is a continual air flow to cool your components.
both should blow into the case your case vents should handle all incoming air displacement
release all obstructions and create a air flow circuit .If you can remove the the band(wich cover the cd location on the front of the case) wich is near your dvd-cd.Put the both fans to exhaust eject the air from your case(the dust who came from the room must be exhausted outside from case) .
I prefer you to make both of them blow out ....





Because the graphics card generates to much hot air inside it's better to consider removing the hot air out....