How do I decide which fans are Input/Output?

Solution
Fans only ever spin in one direction, it's not something you can change. Air goes in the pretty side which has a nice view of the blades and out the ugly side which has the supports, wires and sticker with all the numbers and copyright stuff printed on it.
To make a fan intake you mount it in the front where the pretty side is facing the front, for exhaust fans that's the back and top and you'll mount where the pretty side is facing the inside of the case.
The normal setup is to have the two front fans drawing in air, preferably with a filter.
The top and rear should be exhaust.
You can verify the fan operation direction by dangling a tissue in front of it.
If you have it wrong, remove the fan and flip it over.
 

Thanks

 


If there isn't usually the back of the fan(has the supports and wires is the exhaust side, worst case run the fan and feel the air movement with your hand or a piece of tissue.
 
Fans only ever spin in one direction, it's not something you can change. Air goes in the pretty side which has a nice view of the blades and out the ugly side which has the supports, wires and sticker with all the numbers and copyright stuff printed on it.
To make a fan intake you mount it in the front where the pretty side is facing the front, for exhaust fans that's the back and top and you'll mount where the pretty side is facing the inside of the case.
 
Solution