I feel like you could place it on either side of the fan as long as air is directed to go through it. My personal intuition is filter then fan but I don't see a

I feel like you could place it on either side of the fan as long as air is directed to go through it. My personal intuition is filter then fan but I don't see a reason it couldn't go the other way. I wonder why most devices place it on the intake though. Maybe to prevent dust from getting inside a device, but even then it'd only protect the fan from dust. Hmmm...