Regulatable „put on top“ VOC Filter with recirculation/exhaust air switching

With this project i would like to improve the air quality in the room, my 3d printer is working.

I wanted to be able to switch between recirculation mode and exhaust mode, to decide based on the used material, to use as much filtering as possible (exhaust mode), or to keep the chamber temperature up, with recirculating the air. Also i wanted it to be powerful enough, long lasting and easy adoptable for different types of chambers.

So the only thing this filter requires is a 80mm hole in the top oft he chamber. It soaks in rising air, filters it through a hepa filter, then filters it through active coal, and then either blows it through the exhaust, or circulates it back to the chamber (in radial direction, so that there is only minimal moving air on the print bed.

I printed from ABS and 90ShoreA TPU, so that it should be able to withstand high chamber temperatures. The material used for printing should cost less than 10€. I do not recommend to use less temperature resistant material (such als PLA) for this project. Ideally use non flamable material variants. Do NOT use PLA for this project!

Part list: A: Gridplate B: Housing C: Fan seat D: Deflector E: Fan (10.2€ https://www.amazon.de/dp/B0GQTN83BN ) F: Damping sheet G: Cap H. Active coal (in my case i used 360g, big enough not to fall through the grid, which has gridwith of 2.5mm) J: Grid cap G: Control ring H: Nut M6 I: M4x20 hex head screw J: Sleeve K: Knop L: Outlet seal M: Outlet N: HEPA Filter (1€ per filter https://www.amazon.de/dp/B0FY2JRR8Z ) K: Inlet

Assembly:

1. Put gridplate A on housing B
2. Put fan seat C on housing B
3. Put Deflector D into fan E
4. Put Fan D on housing B, and guide the cable through the cable hole next to the deflector
5. Put the damping sheet F into the cap G
6. Tighten the cap G on the housing B (do not overtighten, the cap will clamp the fan between the TPU slices
7. Turn the filter upside down and fill in the active coal H
8. Close the coal compartment with the grid cap J
9. Hold the grid cap in place and turn the filter upside up
10. Shake the filter a little bit sideways, so that coal dust and little pieces can fall down, but will not pollute the interior of the filter
11. Turn the filter upside down again
12. Insert the control ring G into the housing (chamfer towards interior, screw bore in the position, so that you can see it in the slit of the housing.
13. Insert the nut M4 H into the control ring G
14. Put a M4x20 Screw I into the sleeve J
15. Put the knob K on top of the sleeve (could be glued, if it does not clamp)
16. Wind the knob assembly into the slit of the housing B in the bore of the control ring J
17. Check if the control ring G can be moved by moving the know sideways (otherwise you might sand the pieces until it fits to your demands)
18. Put the outlet seal L on the housing B
19. Wind the Outlet into the housing B
20. Insert the HEPA Filter N into the inlet K
21. Wind the Inlet K into the housing B Now you should be able to connect the power supply of the fan to the power socket and do a test run. The filter should soak in air through the HEPA-Filter, soak it though the active coal and then be pushed by the fan into the outer inerior part of the housing. Depending on the position of the knob, the clean air should exit either through the exhaust or through the outlet.

Functional test: I swichted on the filter and put a receipt agaianst the air inlet. Then i regulated down the power of the filter, but the reciept kept in position even to the lowest power. Only after switching off, the receipt fell off. If i switch to exhaust mode, you can feel the air being blown outside. During recirculation mode i can barely recognize any flow of air at low power. So, seems to do its job.

Disclaimer: IMPORTANT NOTICE – PLEASE READ: This is a private DIY project. Replicating and operating this filter is entirely at your own risk. The author assumes no liability or warranty for the accuracy of the instructions, the functionality of the design, or for damages of any kind. This explicitly excludes liability for: • Health Risks: This filter is not a certified safety device. It does not guarantee the complete removal of toxic gases, volatile organic compounds (VOCs), or ultra-fine particles generated during 3D printing. Using this device does not replace proper room ventilation. • Electrical Hazards: The integration of power supplies (230V to 3-12V) and fans is the sole responsibility of the user. No liability is assumed for short circuits, cable fires, or electronic failures. • Property Damage: Any damage to the 3D printer, surroundings, or resulting from fire hazards is covered by this disclaimer. By downloading and replicating these files, the user agrees to these terms.

Category: 3D Printing