Yet another spray booth question.. or many questions

I found your post very interesting and informative. Thank you. I will be building a paint booth later this spring. I do plastic models and restore and collect rc vehicles. I got alot of great info there. 

If it's vented outside, I wouldn't worry about high performance filters. Set it up with a furnace filter to keep solids out of the fan/ducts and blow it outside.  The quantity of VOCs generated by airbrush painting are minuscule compared to industry.  Is it possible to vent out a window at her friend's house?

I also use furnace filters. Rather than pressure (furnace filters do not have much of a pressure drop) I go for flow.  100 cfm works for me for a reasonably large booth.  I use a muffin fan- cheap, small even for that flow, and easy to mount.  I have a window in my shop and built a little board that fits between window shash and bottom of window with a hole an dryer vent fitting on it for corregated hose.

When I built my garage spraybooth, I originally considered doing a downdraft design and incorporating it into one of my workbenches. I was hoping to have it double as a sanding table but, as you surmised, the two purposes aren't very compatible.

I found this post informative. Maybe you can adapt it to be portable. https://www.reddit.com/r/modelmakers/comments/l54o2e/built_a_downdraft_spray_booth_into_my_workbench/

I second the opinion that the low amount VOCs generated by airbrusing don't warrant fancy filtratrion. Pushing them out of the house is good enough. I also second the comment to concentrate on the cfm rating of the fan and a high-efficiency HVAC filter. Filters are consumables in this situation, so designing to use cheaper, readily available HVAC ones is a good idea.

I didn't see any mention of what kind of medium your wife will be shooting. Acrylics aren't a big deal, but paints with more volitile bases (like lacquers) can create an explosion hazard with certain fan designs. If the motor is in the airstream, the motor brushes can create sparks that might ignite highly flammable VOCs. The solution is to use a fan with the motor removed from the airstream (e.g. - squirrel-cage designs) or invest in an "explosion proof" fan. I went with this something like this - https://www.amazon.com/Explosion-Industrial-Ventilator-Extraction-Ventilation/dp/B08KGFM9BC 

My design has the fan mounted in the garage wall with an HVAC filter covering it, but that's not the direction you're going so I'll leave off here.

Good luck and I hope you'll post pix of whatever you end up building!

Appreciate the reply.

After a week I was beginning to wonder if anyone saw my post.

My wife is going to be using mostly acrylics, but lacquer and rattle cans aren't out of the question. As well as UV resins, hot cutting foam and I might use it for some soldering etc

Now that xmas is over and she has opened the presents, we have had a chance to determine if she wants it to be portable, thankfully no. So direct venting over fancy voc filters is a bonus.

Appreciate the link, will investigate it later today.

I made mine out of foam core and a masonite floor. Updraft to sit up against the kitchen range hood. I use double funace filters. Then there are the range filters. Basically nothing comes out but air moves. Everything is trapped by filtering. I run the hood on low or medium speed. But it needs to be baffled to the filters or you get more and larger dirt falling than was caught, so the filters sit above the baffle, dropping them in from the top.. It served it's purpose when I shot enamels.

On the other hand I'd just as soon not use it , for acrylics and lacquers I'd just as soon shoot into a lined trash can with model stuff.I use a respirator, any left over fumes are gone in ten minutes anyway with model lacquer. Enamels would get the booth but I rarely use enamel any more since the advent of decent acrylics and great model lacquers, 50-50 if to use the booth or go outside when I do use enamel. Then enamel goes right into the dehydrator for a few hours. And my wife's art work is much too large for a hobby booth, I clear coat her work for her either using an exhaust fan or move outside with it. I use fast drying lacquer or acrylic varnish depending on weather and humidity for that. She paints in acrylics, she doesn't need a heavy seal coat. But she does need control on sheen, so that's my duty to deliver what she needs in terms of sheen.. If she's painted it dead on already I have to mix and apply a blend that will dry neutral in a couple of coats.. Anyway, doesn't work with a hobby booth.

Hello ..oldermodelguy ..it's always a good idea to have the vent go outside no matter what paint you or your wife's using .  Acrylics are either water base or alcohol..and enamels solvents. it's the fumes you have to worry about .I build.t a large spray booth for that very reason ( drying after I sprayed my model ) the heat of the light will do the rest ....keeping the fan on 

5high

You may want to see this thread about a home built spray booth

https://cs.finescale.com/fsm/tools_techniques_and_reference_materials/f/18/t/162753.aspx

Here's some pics of my spraybooth that I built about 15 years ago out of a kitchen cabinet I found along the road one day. A cheap $2.98 furnace filter and a $50 exhaust fan from Dayton, Model 1TDR3, 273 CFM. I use mostly Acrylic paints, but I do use lacquers and enamels at times, large spray cans. I work in my loft, which looks out over the living room. My wife has never smelled any paint fumes coming from there. Odors go out the window and particulate matter collects on the filter, if there is any. There shouldn't be much unless you're running the airbrush open too far or standing to far away from the model. She made the sheer curtain for the booth so I could leave the fan running for a while after painting to help in drying and keep any dust from getting on the wet paint. When she sees it getting dirty, turns grey from the dust, she takes it off and throws it in the wash.  When I'm going to paint, I put the board with the dryer vent in the window opening and close the window on it. When done take it out. No muss, no fuss. Change the filters once a year, now $3.25. 

https://photos.app.goo.gl/JUnhMnvkHFTbMxMP8

Stay safe.

Jim