A broken computer power supply (PSU) can have perfect fan and fine casing to become a soldering fume ventilator. I am not calling this one a "fume extractor" because the filter is kind of symbolic and hardly cleans the bad stuff away very well. The fan does not seem to be able to push air through a thick filter anyway but pet store charcoal filter should be okay - and I strongly recommend getting one. It definately does drive the concentrated fumes another way comapred to coming straight up to my throat as happens without a fan.

Turn volume down before starting video - ugly noise :)

Things you will need:

- A (broken) computer power supply that has a big (working) fan.
- 12V DC power adapter (I use my "lab bench power supply", made of another PSU - old but working one)
- A filter - if you have charcoal filter, great; I will show how I improvised a filter from cotton cloth, but I don't have any idea if this does extract anything or not.
- Some kind of soft net - like the bags in which mandarins or other fruits are sold
- Thin cardboard - cereral box for example
- Tape

- Tools: screwdriver, scissors, soldering iron

Step 1: Dissassemble the PSU

- Open the PSU casing and detach the electronics from inside. Be careful to not touch the big capcitors connections with your hand, you would not like it. Shortcircuit them with screwdriver instead - keep your eyes covered at that moment.

The PSU I used had a fan that drew air into the PSU casing so exactly right. It also had enouch holes (in my opinion) on one side.

- Keep the PSUs switch and cut its wires as far from it as possible. Also keep the fan wire intact.

- Desolder the other side of fan wire connector off from the PCB.

Step 2: Make Electrical Connections

- Find out which wire has to be positive for the fan to work. Mark it onto the connector you desoldered from PCB. Also find out which wire from your 12V power source is positive.

- Solder the positive pin of the connector to one of the swich wires. Solder the ground from the power source to other connector pin. Solder the positive from power source to the swich. Isolate the connections.

* Using the connector from PCB makes it easier to mess with the filter assembly and changing the filter in the future, as otherwise the halves of casing would be quite uncomfortably closely attached to each other.

Step 3: Make Filter Holder

Cut strip(s) from cardboard that have the same width as fan frame depth is. Fold it/them around the fan frame and use tape to keep it together. They should fit nearly snugly - the net (which is probably thin) must fit inbetween the fan frame and cardboard. Cut a slot for the fan wire if needed.

Step 4: Optional: Make a "filter" From Cotton Cloth

As I already said in intro I have no idea if this kind of thing removes any of the bad things from air or not. I recommend everyone go buy a charcoal filter from pet shop. I know I have one lying around somewhere, but I could not find it and so I do not want to buy another, but I will upgrade my ventilator as soon as I find that lost filter. But until then this improvisation makes me feel that at least I'm doing something for my health. And I'm sharing the idea with those who refuse to or can't buy filter - in slight hope that it might help a little.

So, to make the "filter" you need some fireplace with fire.
Find a 100% cotton cloth and some aluminium foil. Cut piece of cloth that is a bit bigger than the fan and wrap the foil around it.

Place it in fire (on glowing coal). The package can swell and some flames can come out from the folds. I kept it in fireplace for 2-3 minutes until the flames stopped and nothing seemed to change any more. Take it out, but be warned - it does not smell good in the beginning, better take it outside, open the package and let it stay outside for a while. Mine was a bit fragile, but stayed together enough for the purpose. If it comes out too fragile then I suggest try again with less time in the heat.

Step 5: Assemble the Filter Into Holder

- If you have proper filter then lay it onto the fan (on the inside of PSU casing). If you have an improvised filter that does not stay together too well then put a net for first layer and then the filter.

- To keep the filter in place cover it with net and put the cardboard thing around the fan so that it holds the edges of the net.

* I also tried to put there a layer from paper napkin to catch some solid particles but then it seemed the air was bouncing back from the filter too much and I removed it, I didn't really do a smoke test for that setup to be honest... Try and see what your fan does if there is one more layer in the filter.

Step 6: Final Touch

I also tried to make it easier for the air to make the turn inside the casing and taped a piece of bent cardboard in there. And because I felt air bouncing back from the filter I taped the edges around the fan grille where it mostly seemed to be coming from.

Connect the wires and test if the fan still works. Then close the casing and ... to the soldering, this time bit healthier way.