Noob fan installation

[eco_bach]

Hi,
Can anyone tell me if there is a way to determine fan air flow direction BEFORE you install and connect power?

 

[Janus67]

Sometimes there is an arrow.

Otherwise I've found in all of my cases that the fan airflow went through the side that has the plastic pieces/wires on it

 

[trents]

Every fan will have two main parts, the propeller and the housing. The housing has four struts on one side that support the propeller hub. The other side of the fan is open. Air will flow from the open side to the strut side.