sd3dprinting - It is kind of a tradeoff. Best if you could exhaust out, but that will induce drafts so you would need to be running enclosed printers. Properly placed recirculating charcoal and HEPA filters will work with unenclosed printers but you need to change them out every 3-6 months.

We designed a $400 filtration charcoal+HEPA filtration system from off the shelf components for our laser cutter and 3D printers. It works well for a 300 sqft garage sized area. Only problem is it is pretty loud unless you put it inside a cabinet. We built a custom rolling sound dampening cabinet for ours since we are in a retail location, but if you are sticking this in your shop/garage it shouldn't be a problem.

sd3dprinting - Also to be noted, exhausting straight to atmosphere may be illegal in your area. It certainly is here in California...

tjones - ahh interesting. I like the idea of a rolling sound cabinet. might be a weekend project.

thanks for your input.

do you remember which stock components you used?

niju9 - I am searching for the same Ventilation in your 3D printer and got some idea from https://aboutallpet.com/best-electronic-dog-doors/ what do you think