Pocket fresh air filterer project!

At the start of June, I began a personal project to tackle a big global problem: bad air quality in areas where pollution is present. I wanted to create a mobile air filtration system that could double as a mask, allowing people to breathe clean, filtered air while living in extremely polluted places. I envisioned a battery-operated unit that would draw foul air in, clean it and then shoot it out through a tube that could attach to a mask. It’s akin to powered air-purifying respirators but is cheaper and more readily available.

First things first, I ordered a small USB-powered fan from Temu. Lightweight and small, perfect for a wearable trinket. I dismantled it and, with an exacto knife, sliced it in half as nicely as I could to separate the motor from the air flow parts. Next I had to create a custom case to house the fan, protect its components and channel the airflow through a filter and nozzle to the mask.

cut up fan

I had a few teething problems, particularly around measurements. I didn’t have digital calipers, so I was measuring with a straight-up measuring tape, which made it difficult to cater to precise sizes. My first case I designed by wild guessing and reviewing the design 3D modeled a cap to cover the fan motor housing but it didn't look right and it was a very tight fit. It was a “perfect fit” that didn’t fit at all, because I didn’t leave a little wiggle room for tolerance.

1st iteration

Fitment

With the next version, I simplified the form and redesigned the mounting to have a little wiggle room. I reprinted the cap with a larger internal diameter and more gradual curves. This time it was nearly perfect, but just tight enough that I didn't want to force it together and potentially snap something on the plastic or fan.

2nd iteration

2nd iterations poor fitment

Learning from that, I made a new round of changes, adding around 0.3-0.5mm clearance just to account for 3D printing variances and alignment. This version worked great. The case was very snug, yet easy on and off and it provided a nice stable mount for the remaining parts.

3rd iteration

3rd iteration fitment

for my fourth iteration i intend on sanding down the imperfections of the fan, because the knife and lighter didn't do that great of a job slicing through it. Once that down i have to see if it fits in the 3rd if not then there will need to be some more upgrades to the dimesnions.

With the housing prototype complete, the filter mount and nozzle connection are next. I'm going to get a small HEPA or an activated carbon filter and put it in the flow of air, and create a nozzle for a flexible hose so I can point it at whatever I'm working on. This hose will deliver the filtered air to a generic mask with a one-way valve, allowing the user to breathe clean air without the additional strain.

I've learned about tolerances, trial and error, and the difficulties of prototyping when one does not have every single tool under the sun! It’s been a very hands-on engineering type of experience, and I’m eager to continue to make it better.