Active carbon scrubbers need a lot of mass to be effective against VOCs. There're plenty designs to add scrubber to Q1 PRO, but I'm not sure how much they really help. But even a small HEPA can do a good job filtering small particles, so I decided to tackle that. 

The problem with HEPA is it restrict air flow so much it's hard to push air though it without leaks. So I had to mount it in the chamber in front of the fan. 

It might interfere with the print head a little bit but shouldn't be too much a concern. It's mounted with the same screw the ventilation fan uses.

Since Q1 Pro has heated chamber use at least PETG

Filter used: https://www.amazon.com/Electropan-Filter-Replacement-Robotic-Cleaner/dp/B0782T7L6P Just push it in, it's tight for sealing.