This is a simple collar and locking plate that fits a Xiaomi air purifier filter element for the 2-series air purifiers easily found across Asia, Europe, and elsewhere. The hole fits a 96mm/4 inch fan (best compromise between airflow and low noise IMO).

Meant to be  used to repurpose a used but still working Xiaomi 2S, 2Pro air purifier filter element for air filtration when 3d printing in an enclosed space or for expelling resin fumes externally.

Secondarily, in many countries there is seasonal burning, wildfire, or a general period where air quality is at toxic levels.

This is a cheap way to make a purifier or positive pressure system using easily sourced filter elements with a 4-inch inline fan with a 96mm diameter “nozzle”.

The filter adapter can fit other brands that have at least a 96mm opening on top and an outer diameter of 200mm.

The 2 plate design allows for filters of various heights to be used.

Use bungee cords, tie straps, cable ties or any other method to tie the two plates together to maintain a good seal.

Air Purifier Configuration

A 4 inch fan is a good compromise for airflow and low noise. Plop in a 4 inch fan into the opening.

Positive Pressure Fan Configuration

Sometimes there is too much pollution and running air purifiers simply creates a volume of low density pollution inside your living space that still allows external pollution to creep into.

Attach a 4 inch duct to the top of the inline fan and use this window vent or something similar to pipe fresh air into your house.
This will create a low-level positive pressure within your house to mitigate dust and other particles from creeping into your home through window frames, door frames, cracks ceiling installed light fixtures. Mileage may vary depending on how big your home is.

For larger homes, using an 8 inch fan with this collar (I'll upload it and link it soon) significantly improves airflow but will also quickly introduce hot/cold air into any climate controlled house or room.

Leak-Proofing

For better performance, use rattle can moisture sealant to spray down the printed parts to seal up any printing imperfections.
Also, using rubber window seal strips or printing this gasket in TPU helps to prevent leaks as well.

Pre-Filter Wraps

These generally help to extend the life of the filter element, especially for the Positive Pressure Fan configuration.

This is a setup I had used for the past 6 months. Where I live we have a “burning season” between February and May. I have now upgraded to an 8 inch fan setup and have moved the 4 inch fan with a fresh filter installed for indoors air purification in the kitchen where I do not want to expose more expensive purifiers with sensors and screens that can get gummed up in a kitchen environment.