I used for my first time a PS filament (http://www.owa3d.com/en/); the result is a very light case, with about the same difficulties to print as an ABS filament. Any other filament should do the job. The hardest part to print is the exhaust door, due to its shape (without any flat face). There is a circlip to put inside the carbon case, used both to lock the nuts into their holes and to press a fine net against the case exhaust to prevent the leaking of the pellets into the fan. It is intended to be rotated in order to be locked into position. I used a 3 pins fan for its ease of speed regulation (using a simple potentiometer). A PWM fan could be used, but needs a special regulator and his only advantage is to allow lower speed, which is useless for a filter that requires some power anyway. The door on the exhaust diverts some of the flow back inside the enclosure, and is supposed to have adjustable positions, but I actually always let it wide opened. The following parts are to buy : - a HEPA filter : https://www.amazon.fr/Filtre-Hepa-H13-King-R%C3%A9f%C3%A9rence/dp/B00CZSGMB6/ref=sr_1_7?ie=UTF8&qid=1511712102&sr=8-7&keywords=filtre+hepa+h13 - any active carbon pellets (like https://www.amazon.com/NTnormal-Activated-Charcoal-Aquarium-Canister/dp/B00WW42ZS2). I used the pellets bag to make the filter between the pellets case and the fan. - a fan: I bought a silent one (https://www.amazon.fr/NF-A6X25-FLX-ventilateur-refroidisseur-radiateur/dp/B009LEKGGE), but a more powerful and noisy can be used as well.. - 6 m4 nuts. - 2 m4 computer case screws (for the case). The can be replaced by any other screws; I used them because they were laying around and allow a manual opening... - 4 m4x40mm screws to attach the case, the fan and the exhaust together. Do not hesitate to leave comments or questions!