I built this over a weekend, and it has been running in my bedroom for about two weeks now. According to the graphs in my Home Assistant, it’s indeed purifying the air!

The filter had been collecting dust (sitting on a shelf) since a previous attempt at building a “smart” air purifier that I lost interest in. I might’ve bitten off more than I could chew.

This time, I decided to keep it simple and went to Bunnings to grab a cheap pedestal fan, which I gutted. Using a caliper, I measured the mounting points and started modelling in CAD. Other than the fan’s internals, the only hardware I used was a few M3 and M5 Phillips-head screws.

Here’s the Onshape project (warning: I don’t know CAD).

There are some glaring issues, the main one being that the air hits an almost 90-degree wall on the impeller housing before entering the lower half. I’m hoping to improve the design over time using real data and maybe CFD. I used smoke to test the suction, went through a couple of impeller designs, and settled on this one.

I have an HA automation that turns the purifier on (actually, a smart plug) when the room’s air quality is “poor” and turns it off when it’s normal.

The filter is friction-fit at the moment and doesn’t have a cover around it. I’ll make one later.