Don't mean to hijack the thread, but I have a similar question.
I have a makeshift darkroom in my bathroom, it's ventilated with a normal wall mounted bathroom fan. But I want to have a fan above the trays on my workbench to suck out the polluted air right away.
So I'm thinking about buying a used kitchen fan, clamp it to my workbench about 1 or 1,5 meter above it and connect the air outlet to the wall mounted bathroom fan with a ventilation hose/tube. The used kitchen fans are cheap, wide and with 230V plug&play. And maybe supply this with a air freshener with HEPA filter.
Does it sound like a good plan?
For example a fan similar to this
http://cache.finn.no/mmo/2011/7/10/5/295/312/25_879810002.jpg
Those kind of kitchen fans are not suitable for duties for which they were not designed, as typically the instruction manual says.
That means that they can overheat if you let them on for hours continuously (I don't know how long would you let them on) or, who knows, that they can make a sparkle when you don't expect one (careful with that propane/butane mix

) and other sort of unexpected failure (maybe taking fire).
One of those kitchen fans failed on me quite brutally one day. It had a short, the house was suddenly in the dark, and the fan become burning (all the kitchen oil around it, that is). I couldn't reach the flame as it was behind the metallic grid and it was of the kind that needed a screwdriver to be removed. I could not launch water from down up as the grill stopped it. Needless to say, the entire kitchen stuff was inside wooden furniture. The fan exhaust into a natural chimney. I seriously feared a fire, picturing the scene in my mind: the chimney would keep the flame alive, the wooden kitchen could take fire and within a few minutes I would have some hundreds degree in the room.
I went to my neighbours and told them to call the fire brigade. Not prompt people, they didn't call the fire brigade. Two of them came with me, when we entered the house it was very smoky. I went inside the kitchen just in time to see the small flame extinguish itself for lack of oil.
My mother (when she used that kitchen, for many years) had removed the filter and tons of oil had accumulated inside the motor. She never used the fan anyway. But the oil vapours went to the fan anyway. I used it, instead.
I know it was not the kitchen fan fault, but since them I don't trust the contraction.
Fabrizio