my DIY attempts for dealing with wildfire smoke

In 2020, wildfire smoke on the west coast was horrendous. I had purchased an air purifier but wanted more and they were exorbitantly costly. I figured they were just a fan with HEPA and carbon filters so tried to make my own solutions. TLDR, none really worked well. The devil is in the details and by the time I realized some of the issues, the smoke was already subsiding.

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Here was the first attempt hahhaa. Turns out the filters are really dense and air has to be really pushed through to get a high CADR. When there’s other paths the air can take, the air doesn’t go through the filter as much.

Here’s attempt two. I bought a cheap box fan, kept the fan in the box, and cut a rectangular piece out from the box to fit in the filters. I cut slivers in the back to allow airflow in which gets blown out through the filters. This also didn’t work that well. I think there were still too many escape areas for air and also some air still blew back out from the back sliver cuts.

The next attempt strived for maximal simplicity and fewest parts. I removed the top from a smaller circular fan and would place the filters on top of the open fan, covering the entire circumference. When I had purchased the fan, the top didn’t seem slightly curved and protruding outwards, but it actually was. This made it difficult to flatly place the filters on top.

This was my attempt at venting CO2 from the inside without letting the micro particulate matters and some VOCs get in from the outside. I wedged the filters between the sliding window and wall, and had to cover the rest of the opening with a cardboard cutout wrapped in plastic trash bags. The plastic trash bags seemed more air proof than the cardboard and also would have loose excesses that can be used for taping against the window/wall. This also didn’t work. Smoke pollutants from the outside continued to get in.

Abstractly, this is how I had thought about addressing the problem:

1. I need air.
2. Preferably the air is somewhat fresh (low CO2, VOCs) and doesn’t have pollutants from the wildfire smoke.
3. Polluted air comes mostly from the windows or doors and some walls with discreet cracks.
4. Air is fluid, moves according to pressure, and each particle is extremely small. Will be very hard to manage with stiff materials. A substance that has the ability to “fill in” would be helpful. Fluids that harden may be effective at covering the cracks.
5. Ultimately decided that putting some positive pressure on the wall may do the trick. Fight air with air. Tested by having a fan blow air against the wall, and it reduced the pollutants coming in noticeably!
6. For the issue of polluted air form windows and doors — if I wanted to keep the ability to vent out CO2 and indoor VOCs outside, I’d need some filter between myself and that outdoor air. I could filter at the point of entry, point of inhale, or anywhere in between. (It’s fun to think about the in between option since it’s less standard).
7. Outside filtering, I could also consider chemical conversion (e.g. with algae farm) or artificial replacement of desired air (e.g. mask that’s connected to small tank of compressed breathable air). Turns out algae farm solution will require a lot of algae to make a difference. And artificial air from a tank will likely be more unhealthy.

Also published on my substack.