By running off mains, the fume extractor can run 2X fans at full power.
And all of the parts are easily available, maybe even stuff you have lying around.
The shell of it is an empty ATX power supply.
I'm keeping it short and simple, because I'm presuming that whoever wants to try this has basic knowledge of electricity.
If you don't know what you are doing, then this project is a bad idea - 220V AC CAN KILL YOU. If you wire it up wrong, you could short circuit to the metal shell and....
Hope you enjoy!
Step 1: Parts
Apart from the box, you'll need:
1x DPDT switch, rated for mains voltage.
1x 220-12V transformer.
2x 3300microF polarised caps, rated for 25Volts or more.
2x 12V fans
1x bridge rectifier, or 4x power diodes.
1x three-prong socket like the one that computers use.
Lots of wire.
Screws, bolts, nuts.
Drill with metal bit.
Clear pieces of plastic for gluing over the openings of the box.