Interesting solution. It does seem small - a 1:24 car body or 1:72 airplane would hardly fit in there. Also, you're not worried about blowing fumes back into the room? Or are you using ducting to vent the fumes outside? And I see the fan is a standard axial one. Wouldn't this create a fire hazard (if you use flammable paint or propellant)?
The overall idea is a good one - it's certainly better than nothing at all, especially for smaller models. But the fan/ducting design is a problem Most electric motors use the carbon brush and copper commutator, and carbon particles from the brushes certainly do wear away and cause high voltage arcing - i.e. sparks. Also alcohol is indeed flammable. The solution is to take the fan out of the airflow. How? That's down to duct design - an 'L' shaped arrangement usually works, with the fan at the juncture blowing down the long arm of the 'L' creating suction at the end of the short arm. Find a good source of info - adding venturis will increase the airflow for instance. It's probably out there on the net, but hey - I have a perfectly good window to spray out of, so you'll have to find it yourself. :) Plus its a creative use of resources that would otherwise go to landfill. Good one Olle. Chek
The "Hepa"-filter is an active filter which seems to be good at soaking up fumes from at least akrylics/alcohol. There is no smell at all. Placing parts that's been "washed" with oils diluted in White spirit inside the booth and starting the fan will also take away the smell.
A venting duct will be attached when I switch to my new room. I see that most as a way not to have too much dust lifting and circulating in the room.
About fire hazard - never heard about it happening. I spray akrylics and dilute with alcohol. As mentioned earlier, most of the fumes stays in the filter and what's left can't be much. If I was able to get a concentration of fumes that could be lit by a spark from the fan i would worry about it no mater which fan I used. I personally don't think it's that likely an explosion or fire would start just because of the fan. It would have happened before - I think.
This is just an alternative to nothing at all. If you can afford, or can manage to build a "regular" booth that will probably be best. But this is cheap, easy and it works for me.