Darkroom Fan - homemade or not

[Toyon]

The fan should be mounted low as the chemical vapors tend to be heavier than air.

[Jason Greenberg Motamedi]

Rather that using a bathroom or kitchen vent for something that it was not designed for I would buy a squirrel cage fan (250-1000cfm depending on the size of your darkroom) from one of the "indoor garden" stores, build or buy a rear exhaust vent hood (see below) and use use 6" PVC or ABS pipe to exhaust it all. If you really don't want to vent the air out of the house, I would consider using a big activated carbon filters (again, at an "indoor garden" store) to swallow the fumes. However, it will probably have to be replaced every 6-12 months, so it may be cheaper to just lose the heat.

Read through Jon Edwards's notes on ventilation before making any purchases; http://www.eepjon.com/Drvent.htm

[Peter Collins]

Yet another alternative:

I went to our local PC repair shop and bought a 4" computer fan and a power supply (PS) from their junkpile for $16. I put up the darkroom wall (it is in the basement; conc block on 2 sides) with 2x4 framing to make a box about 5x5 inches inside dimensions, sheathed it, cut a hole in the sheathing on both sides, and trimmed the hole with casing.

Now I had a hole; I slipped the fan inside, fastened it, and ran the DC leads into the PS inside the darkroom. The PS sits on a shelf and its cord goes to the 110.

Voila.

Reads more complicated than it is. You just work out the finished idea before you hammer, nail and saw.

If you have a PC in trouble and find yourself in Ann Arbor, trust MCRS (Micro Computer Repair Specialists). They have seen it all.

[pocketfulladoubles]

Simple, for supply air use a 6" in-line hurricane fan and about 10-ft of acoustical flex duct. They can handle a decent amount of static pressure, plenty for what you need, and won't fail. A good brand like Grotek (guess who uses these things the most ;-) The acoustical flex duct should start at the bottom of a stud wall and run up along the studs to a diffuser in the room near the ceiling. Do not select a diffuser with opposable blade dampers, it should not have any dampers at all really. That stud bay where the duct runs should be filled with R13 batts. Put a return grille down low and vent through a light trap. You may want to avoid any fiberglass in the return (exhaust) stream to avoid moisture entrapment. Oh, and don't support the fan on any framing member of the room itself - you're asking for vibration noise. If you cannot avoid this, use neoprene mounts with a static deflection rating of about 0.2 in at least. Some may tell you to install the fan at the end of a ducted exhaust and "pull" rather than "push" the air. I'm not sure it really matters for such a small purpose. If you are moving way to much air, you can get a rheostat and slow it down.