DIY Cannon: Better, Faster, Stronger

Ever since I started my DIY filter experiments, I’ve been wondering whether I could create a super DIY by using a stronger fan. In the past three months, my collaborator Anna has helped me test a half dozen different fans. She now has a home full of fans:


DIY Purifier Fans Test


After months of tests, one fan has proven itself to be the king of fans. I’m now ready to unveil a newer, more powerful DIY:


DIY Purifier Cannon DIY Filter


Informally I’ve been calling it the “大炮,” the Cannon. That describes how it looks, but also what it does to air pollution. Simply put, this thing kicks butt:


DIY Filter Cannon Air Purifier Test Smart Air


Even when you look at the really small stuff–0.5 micron particles–the Cannon is equally impressive:

DIY Filter Cannon Air Purifier Test Smart Air

Over five nights of testing, the Cannon removed an average of 97% of 0.5 micron particles and 96% of 2.5 micron particles. I think this may be close to the upper limit of how much particulate pollution you can remove from your air with a home-use filter.

(Update: for more Cannon room tests, check out tests with an added carbon layer and tests on the medium and low settings.)


DIY Filter Cannon Air Purifier Effectiveness


What’s the difference between the Original DIY and the Cannon?

In 8-hour tests, the Cannon removes 4-13% more particulates. 

In the overnight tests, the Cannon is removing somewhat more particulates–especially the smaller 0.5 micron particles.


DIY Filter Air Purifier Effectiveness Test


Remember, this is an average, so the difference is larger on very polluted days and smaller on clean days. (You can see the data for individual days in the raw data at the end of this post.)

The Cannon cleans faster.

Because the Cannon circulates air a lot faster, it reaches those numbers faster than the original DIY.

This is harder to illustrate than average effectiveness, but you can see it clearly in our controlled tests. In the controlled tests, we burn a source of 0.5 micron particles (a stick of incense) in a small closed room. After 20 minutes, we turn on the filter. In those tests, the Cannon is clearly faster:


DIY Filter Air Purifier Speed Test


Now, this speed test is only to demonstrate relative speed in controlled conditions. The speed test room was small–a bathroom. It’s not meant to say the Cannon will clean your whole bedroom in 1 minute. But it does say the Cannon will clean your room faster than the Original DIY.

The Cannon is better suited for very large rooms.

Some people have told me they want to use the original DIY to clean large spaces, like stores and multi-person offices, but the original DIY is not really made for large spaces. If you want to clean a large area, the Cannon has the power to get the job done. (See tests in a 30.5 m2 room.)

Is it still affordable?

The stronger fan is more expensive and heavier, but we’ve still managed to get the price at Smart Air to 450 RMB. At that rate, you’d be removing 97% of your 0.5 micron particulate at just 4.1% the price of the 11,000 RMB IQ Air.

When should I choose the Cannon vs. the Original DIY? 

I would recommend the Cannon for:

  1. People with larger spaces, like large offices or bigger-than-normal living rooms.
  2. People who are very concerned about air pollution and therefore really value that extra speed and effectiveness–for example, people with health problems, pregnant women, and children.

But for most normal-sized bedrooms (<15m2), the Original DIY will still do the trick.

As always, I’m posting the original data and methods below for fellow data nerds.


Thomas Talhelm

Thomas is an Associate 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.

8 thoughts on “DIY Cannon: Better, Faster, Stronger

  1. Looking forward to ordering a filter and using in Thailand. But…

    Do look you have any data on the decibel level of the two different styles of filter (original and cannon)?

    I have a big bedroom that is about 24 sqm and living room about 38 sqm

    1. Hi Pavel, we can certainly ship to Russia! The HEPAs we use are H12 HEPAs, which means they get at least 99.5% of all particles. Send us an email with what you want to get an estimate for shipping costs to Moscow.

  2. Would like to order HEPA and carbon filters, do you have any recommendations for comparable fans to the Cannon that could be purchased in US (Avoiding high international shipping)

    1. Hey Paul, we’re working on an article to make it easier for people just like yourself to find comparable fans to the Cannon, it should be out fairly soon!

      If you’re in the US, then box fans are a very good option for a cost-effective air purifier, just make sure that the HEPA is bigger than the area of the fan. Stay tuned for that new article on DIY purifiers.

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