is there any home made a 120mm fan filter

[hollo]

i made one 2 days ago - ok it probably isn't quite like what you'll be doing but here it is:
this is for the DSL modem and wireless router in our flat. i noticed the modem was getting a bit warm, and our connection would drop from time to time. so i decided to stick a fan on it and see if it helped.
since the filter was going to offer some resistance to the air-flow i decided to make it larger than the fan, it probably ended up with the surface area of about 1.8 120mm fans. it's powered by a USB charger for an mp3 player that broke, ie it runs at 5V. it's made of a piece of stiff plastic screwed into the fan, foam tape insulating the join between the plastic and fan, a piece of polystyrene board as a spacer, and some sticks to stop the polystyrene part from caving inwards from the pressure of the pantyhose stretched over it. the size of the gaps in the pantyhose with it stretched as it is is probably about .5mm by .5mm, ie it'll be letting through 'dust' but stopping 'fluff'. i'm hoping that as 'fluff' builds up on the filter it'll become the filter and improve the filtering power - of course the air-flow will be reduced as this happens, but air-flow isn't a huge deal with this thing.

most of the air blows into the top vent of the DSL modem, while one edge of the fan is meant to blow some air through the side vent of the wireless router and out the other side. the fan's tied in place with string, and stopped from vibrating the whole board by 3 pieces of foam between it and the dsl modem.

i love it