Active Air Filter (HEPA 13 Filter and Active Carbon Pellets)

I initially made this filter to remove the toxic volatile organic compounds and fine particles generated by my 3D printer. It can be, of course, used for other purposes, like filtering the air of a room; just keep in mind it is designed to continuously filter air, not to clean heavy fumes at once.The HEPA filter catches the particules, while the active carbon removes odors.

The box is about 11x11x20 cm big, and contains a HEPA 13 filter and active carbon pellets. The filter is actually a vacuum cleaner filter which seem to be standard, or at least easily findable, and the active carbon pellets can be bought from any aquarium seller, or others.

I mounted a 12V fan, and preferred a silent fan over a powerful one, but you can make different choices. There is a door on the exhaust pipe, used to redirect some of the filtered air back into the printer enclosure (thus keeping a correct temperature inside), which is not mandatory (actually, the exhaust pipe is not mandatory either).

It is difficult to test the filter efficiency without proper tools; at least, the smell inside the printer enclosure is much lighter now that I use this filter...

Step 1: Tools

You will need :

• a 3D printer,
• a HEPA filter (like https://www.amazon.fr/Filtre-Hepa-H13-King-R%C3%A...),
• any active carbon pellets (like https://www.amazon.fr/Filtre-Hepa-H13-King...),
• a piece of Tulle (or any related netting) to place between the pellets case and the fan, to prevent the leaking of the pellets into the fan (I used a bag given with the carbon pellets),
• a fan (60mm diameter, 25mm depth): 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). They can be replaced by any other screws; I used them because they were laying around and allow for a manual opening...
• 4 m4x40mm screws to attach the case, the fan and the exhaust together. Length may vary if your fan is thicker/thinner and if you do not use the exhaust pipe.

Step 2: Printing

The .stl files are on youmagine.

The hardest part to print is the exhaust door, due to its shape (without any flat face); this part is not mandatory anyway. It has adjustable positions, but I actually always let it wide opened...

The other parts are rather simple to print and require no supports. About the filament, 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.

Step 3: Assembly

Cut and put a piece of netting to the bottom of the pellets case. Push four nuts into their holes, and use the circlip to lock the nuts in place and to press the netting against the case exhaust. The circlip is intended to be rotated in order to be locked into position.

Screw the exhaust, the fan and the pellets case together using the four m4x40 screws.

Insert two nuts in the pellets case lugs.

Fill completely the pellets case with the active carbon, and check no pellet goes through the netting and blocks the fan.

The HEPA filter has two lugs; cut them and put it into the filter case. Then screw the filter and pellets cases together. The two screws are intended for an easy access and change of the filter and pellets.

Step 4: Fan Control

You can plug the fan directly to a power source, or add a speed controller if you wish.

I used a potentiometer with switch, that allows to change the circuit resistance, thus the fan speed, and to stop completly the fan.

A more advanced PWM fan could be used, but needs a special regulator; his only advantage would be to allow lower speed, which is useless for a filter that requires some power anyway.

The schematic above is pretty simple.

Step 5: The End

The filter is assembled; there are two .stl files for mounting brackets whether you want to suspend it.

Do not hesitate to leave a comment or a feedback !