How to Make a DIY Air Purifier

Based on my research into how different filters work, I concluded that a HEPA filter is all you really need to fight particulate air pollution in China. Given the fact fancy air purifiers run for 8,000 RMB here in Beijing, and I’m only here for a year, I thought I’d try making my own DIY air purifier.

I give data on how well it works here (1, 2, 3, 4), but here I’ll explain how I made it


1. Buy a fan

It’s important that it has a flat front so that you can strap the HEPA filter to it.

Fans with flat fronts usually have a recessed motor unit, so look for that. Here’s the one I bought for 58 RMB (about US$8.50):

diy air purifier fan


2. Buy a HEPA filter

I first bought this one for 108 RMB:

diy air purifier hepa

Since then, I tested HEPAs from all the manufacturers I could find, and found one that captures more particles and has better air flow. Because I buy it in bulk and ship it through the shop for my social enterprise I set up, it costs less (75 RMB) than that first HEPA I bought. I’ve tested it with my particle counter, so I know it works.


3. Pull the grating off the front of the fan

It helps if you have pliers for this. Then turn the power setting to 3 and pull the knob off.

The knob gets in the way of the HEPA. Without the knob, I turn the fan on and off by plugging and unplugging it.

diy air purifier 3


4. Strap on the HEPA

Use string to strap the HEPA filter onto the front of the fan, and you’re done! Your very own DIY air purifier.

The metal bar in the middle will stick through the filter a little bit. You could saw the metal bar off, but my tests show it doesn’t seem to make a difference. Or better yet, find a fan without a metal bar in the front, like the type I ship through my social enterprise.

diy air purifier 4

diy air purifier 5
Total cost for this DIY air purifier: 166 RMB (US$27). Compare that to 8,000 RMB ($1,300) for the fancy purifiers here in Beijing. I now ship a simple fan and a filter that’s more effective than my original design for 228RMB (US$37) .

Your next question is probably, does it work? See a live test here, how well it works if we use a stronger fan like on the DIY Cannon, or comparison tests with the big brands.

And you might be wondering, “shouldn’t the HEPA go on the back of the fan?” I always thought the answer would be “it works just as well both ways,” but I tested it, and the results surprised me. Click here to read more on that!

P.S. Thanks to Artur Weber for translating the instructions for air-breathers in Portuguese-speaking countries!

Thomas is a new Assistant Professor of Behavior Science at the University of Chicago Booth School of Business and the founder of Smart Air, a social enterprise to help people in China breathe clean air without shelling out thousands of dollars for expensive purifiers.

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