THIS IS A RECIPE
ingredients:1) large axial fan. you want something between 180mm and 300mm in diameter. it is imperative that the fan have a flat outlet side and be rectangular (ie, no standing floor fans). pc case fans are the obvious choice.
you want something fairly low speed, so that you don't have a hurricane running next to you while you're trying to solder, and also so that it's cheap. the size specification is only if you plan on using the same cheap, easy to find and conveniently sized box that i did for the body of the filter.
2) activated charcoal (granules, not powder). incredibly cheap in bulk at amazon. if you don't want to wait, any pet store that sells supplies for keeping fish will sell this in bulk.
3) coarse post-filter medium. since you're already at the pet store, blue bonded filter pads work well. this media will replace the back of the box (to allow air to pass through, since your fan is probably not going to be the greatest at dealing with high static pressure, and it will do some mechanical filtering of the dust you get off of charcoal when you move it around.
4) a permeable cloth container for the charcoal. it's messy stuff, and it needs to be arranged so that as much air passes it as possible. i used a lingerie bag i pulled from a grocery aisle display the day i happened to be building mine. a big old piece of cheese cloth would also work fine.
5) a box. i used a USPS medium flat rate box (not the boxy version, the other one). it's just about the right size and depth, and they're conveniently located in the lobby of your local PO.
6) a shedload of tape. duct tape is good for sealing things, packing tape is good for attaching things (to other things). zip ties can be used when adhesive fails, but unlike tape, zip ties tend to disturb the force, and must be used carefully, young padawan.
theory:activated charcoal works by being chemically attractive and by having an extremely irregular and convoluted surface. what this means is that it has insane amounts of surface area and that all the crap in the flux fumes that would normally coat your nasal passageways and upper respiratory tract will instead coat the carbon, as long as you can get the fumes to get relatively close to the carbon. this is what we use the fan and the box for.
construction:cut a fan-sized hole in one side of the box. cut an exhaust sized hole in the other side. attach the fan to the fan-sized hole. if you want to be fancy, use self-tapping screws or some kind of mechanical fastener. if you just want to get **** done, use some tape. coming off? use more tape! make sure the fan is blowing into the box.
separately, lay out your charcoal bag and fill it with charcoal. partition your bag so that not all the charcoal ends up at the bottom if you hang the bag from something (like the top of a box).
stuff the charcoal bag into the box. attach it to the top of the box so that it's hanging approximately behind the fan.
close the box by taping your post-filter media over the exhaust hole.
FAQ:how do i power my fan? if your fan is AC, attach it to mains power and a transformer if necessary. please don't kill yourself while doing this. if you fan is DC, batteries are good. AA battery holders with standard 9v battery terminals are usually pretty easy to find. if all else fails, most radioshacks are forced to sell this stuff because of some idiot in upper management. if you are like half this board and have a box full of wall warts without things to power, find a wall-wart of approximately the right voltage and wire it to the fan.
what if my fan has LEDs? then it's a party and a fume extractor in one. savor it.
my box keeps toppling over? i actually clamped mine to my desk with some extra cardboard and liberal applications of tape. at the very least, you can use cardboard and tape to give the box a wider base.
does the fan have to blow directly into the charcoal? you'll probably need to balance static pressure of the box with the amount of air passing over the charcoal. if your 10$ axial fan is blowing directly into 3in of activated charcoal, it's probably not going to move enough air to suck the solder fumes away from your soldering iron. one can move the charcoal part of the filter around in the box until there's enough of a low-resistance airway for the fan motor not to be overpowered, but enough charcoal near the airflow for the fumes to disappear into the carbon.
ABOVE: SOLDERING STATION FIT FOR A KING
