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DIYer Makes Cannon Quieter

Bill is an expat living in the hills northwest of Beijing, and he uses his DIY Cannon to cut the particulate in his home.

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But Bill wanted to improve on the biggest downside of the Cannon–it’s a bit loud on high:

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So Bill designed a sound dampening box for the Cannon out of foam blocks:

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There are openings in the front and back to let air through, although my guess is this lowers effectiveness by at least a few percent.

To further cut down on noise, Bill wrapped the Cannon with a blanket:

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With all that padding, Bill measured a 6 decibel drop in noise! If you have a Cannon already, here’s an idea of what that’s like: That’s 2 decibels quieter than the regular Cannon on low (52 db).

If the noise gets to you and you don’t mind a craft project, I sanction it! However, keep in mind two things:

  1. Monitor the fan temperature. Make sure your design does not allow the fan to overheat.
  2. I suspect this will lower effectiveness by at least a few percentage points. I can’t say more precisely without testing it.

Great work, Bill!

 

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Harder, Better, Faster, Stronger DIY

Ever since I started my DIY 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:

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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:

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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:

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

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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.)

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But wait, isn’t the original DIY effective too? That leads to the question…

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

  1. 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.

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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.)

  1. 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:

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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.

  1. 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?

One obvious question is, sure it works better, but won’t it be way more expensive? 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.

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