ooling fans, can they be fitted either way round?

Hi all

First post and thanks for being there.

Something puzzles me and I feel sure someone here will solve the puzzle for me!!

If I use cooling fans to (a) draw warm air out of the case and (b) bring cooler air into the case - does this mean I have to fit fans different ways round to achieve each of those outcomes?

The only thing I notice when for example looking at an Antec 120mm fan I have which is in its original packing is the shape of the blades. When viewed in this way with the Antec circular logo facing me, the blades appear to curve backwards. Is this called concave? And, I imagine when this is fitted to the inside of the case, the logo will remain visible from outside the fan grille, and that the blades will curve backwards in the same way that they appear to me at present.

Perhaps they are all fitted in one way (like described above) and it has something to do with convection currents of the air within the case, and not which way round a fan is fitted to the case.

Be grateful to hear from those of you who know about such things please, as this has always concerned me and I would really like to understand this properly.

Many thanks.