This is a simple filter system for enclosures. It allows you to pull your enclosure air through standard 3M bayonet filters (like on a painting mask) using a squirrel cage fan. I of course make no guarantee as to the system creating a safe breathing environment. That being said, health and safety at my work checked particle counts in my office while I was printing and there was no elevation in particulate levels. I also use filters for organic vapours 3M 60923 and when I print ABS or ASA I can't smell anything in my office unless I open the enclosure door. One nice thing about the system is that uses parts you can easily replace.
I have posted two versions, a 2 filter or a 4 filter manifold. 2 filter should be fine unless you really need to pull a lot of air. You need to print 1 fan adapter, 1 manifold, and the corresponding number of threaded tubes, washer nuts and bayonets.
If you have any trouble with tolerances I would suggest scaling the X and Y directions for the threaded tubes to say 97% but leave the Z direction at 100%. That way the thread pitch doesn't change but the fit will be looser. A useful trick for 3d printed items with threads. They are threaded all the way down so if you want them shorter you can always just chop them down to size using Prusa Slicer (Cut command).
It is designed to be printed with no supports, but the bayonets may need some. I have been successful both ways.
The bayonets have a slot for 1/8" gasket, which I had lying around but you could always replace it with some closed cell foam, print some TPU gaskets or use fun-tak to seal it.
Should you wish to design your own bayonets for different filter brand. The threading is M30x3.5.
Should you wish to design your own fan adapter the manifold opening is 65 mm. Make sure you use a squirrel cage fan (blower) though as you need it be able to generate enough pressure to pull the air through the filters and normal case fans move lots of air but not if there is a back pressure.
I am using a San AceB97 9BMB24G201 fan which I bought through digikey. Though it is overkill and I am usually only running it at about 15%.