With no attachement, take the vacuum and put if very close, you will hear a "wind tunnel" sound as the processor is fighting to suck air, while the vacuum is forcing the air to be sucked towards it instead, sudently you'll hear a "whosh" and all the dust literally blows off as the fan suddently spins the oposite direction because of the vacuum's force. This is most likely because the G force involved in the fan going somewhat 4000rpm one direction instantly switching to maybe 7000 in the other direction shoots the dust right off!
It's a really cool effect, you just have to be very careful not to touch the blades as spinning at this speed can be lethal for the fan (and possibly yourself) if they hit the vacuum and break. But the effect is so cool it's worth the risk.
It does not work with normal 80mm fans though as they are too big, you will get the suddent oposite spin, but not with the "whosh" effect.
Yet Another Fun but Possibly Dangeraus Experiement™.
Archived topic from Anythingforums, old topic ID:357, old post ID:2756