This is my first attempt at a simple air purifier that requires very few parts and the best bang for your buck. 

Model fits standard 120mm pc fans but if they have a rubber cushion like the noctuas fans do you need to scale the arms to 165mm in length.

you do not need to change anything for fans like the P12 Max that do not have a rubber cushion on the corners 

The filter is: Pureburg TT-AP006 true HEPA 

It costs around $24 for a 2 pack on amazon 

I used a simple 4pin pc fan controller. One of the ones that have a knob for changing the speed and plugs into a wall outlet. 

Face the fans to blow away from the filter so it is pulling air through the filter. 

Arm are built for a compression fit so you need to bend them a little.