The Original

For 200 RMB, we'll send you a fan, a HEPA filter, and a strap. Assemble it yourself with the instructions given or choose a pre-assembled unit. Either way, shipping's included.

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The Cannon

Stronger fan, lower particle counts, and faster clean air. If you're looking to clean a larger area, check out our powerful Cannon kit. Same HEPA, just pushing more air through it.

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HEPA filters

HEPA filters are what trap small particles like PM 2.5, and they're not expensive! We buy ours straight from the factory so we can pass the savings on to you.



We think if more people knew how air filters works, they'd think twice about paying thousands of RMB for clean air. Check out Particle Counting, attend a workshop, or:

See the data »

We now have 1 year purifier kits! Enough HEPAs to last a year. Get them here.

Smart Air now available in India! Order here.

DIY Kits: Now with two fan options

The Original

The Cannon

200 RMB

470 RMB

Original Cannon


(average percent reductions, based on 8-hour tests in a 15 m2 bedroom)

The Original

The Cannon

Original Cannon

Purification Speed

(based on a 1-hour test in a 1 m2 bathroom with a source of PM.5 pollution. Get the full story here.)

The Original

The Cannon

Original Cannon

Suitable for normal-sized rooms
(< 16 m2).
Quieter than the Cannon.

Suitable for larger spaces
(at least 30 m2)
and anyone wanting clean air fast.

Check out Particle Counting for more details.

Order delivery. Or takeout.

Are you a small business, school or company looking to kit out your building? Get in touch with us at info@smartairfilters.com and we'll help you work out what you might need for your space.

Original kit: 200RMB


1 fan, 1 filter, and 1 strap.

200RMB or $32 USD.


Cannon kit: 470RMB


1 fan, 1 filter & prefilter, and 1 strap.

470RMB or $74 USD.


Extra filter: 75RMB/85RMB


1 HEPA filter (Original/Cannon).

75/85RMB or $12/$13 USD.


Original DIY 1 year kit: 419RMB

Original 1 year purifier kit: 425RMB

1 fan, 4 filters (to last you a year), and 1 strap.

419RMB or $66 USD.


Cannon 1 year kit: 719RMB

Cannon 1 year purifier kit: 725RMB

1 fan, 4 filters & prefilters (to last you a year), and 1 strap.

719RMB or $112 USD.


Filter multi-pack: 295RMB/335RMB


4 HEPA filters (Original/Cannon) to last you a year.

295/335RMB or $47/$51 USD.


Carbon filter: 70RMB


1 carbon filter.

70RMB or $11 USD.

Extra prefilter: 10RMB


1 pre-filter.

10RMB or $1.70 USD.

Must be shipped with other items.

Extra strap: 10RMB/12RMB


1 velcro strap.

10RMB/12RMB or $1.70/$1.90 USD.

Must be shipped with other items.


For China orders: don't forget to enter your shipping address in Chinese and your phone number in the special information field on the next page! You can also change your order quantity on the next page. Jump down to the FAQ where we have more info on shipping.

For outside China orders: we offer international shipping at an additional cost. Please note that shipping the fans can be quite expensive as they are bulky items. To keep costs down for you, we recommend getting the HEPAs from us and finding a fan locally in your country that will work with our HEPAs. Send us a message with your order requirement and we'll confirm the extra shipping amount. If you don't see your country below, let us know and we'll hound the post office for a shipping quote.

Having trouble with PayPal? Visit our Taobao store for more China-friendly payment options.

Live in Beijing?

Pay in cash at:

Natooke Bike Store

Wudaoying Hutong 19-1, Dongcheng District


Tel: 010 - 8402 6925

(Originals, Cannons and HEPAs)



We run workshops to let people know it doesn't cost thousands of RMB to get clean air. Participants make filters to take home, and we test them on the spot with a particle counter.

Want to host a workshop at your school or office?

Let us know what you need at least two weeks in advance, and we'll start planning:

Keep abreast.

Sign up for our mailing list to hear about future workshops and new filters.

Wechat QR Code

Scan here to follow Smart Air on WeChat

Our Data: Does the Smart Air DIY Purifier work?
Short answer: Yes! Long answer: Keep reading

Let's break down this question into three smaller questions:

  1. Is the air coming out of the Smart Air DIY air purifier clean?

  2. Is the Smart Air DIY air purifier able to actually clean the air in the entire room?

  3. How well does the Smart Air DIY air purifier perform compared to expensive air purifiers?

1. Is the air coming out of the Smart Air DIY air purifier clean?

This is the easiest question to answer, and we do it by holding a Dylos DC1100 Pro particle counter in front of the purifier and watching the numbers drop. Here's a video of Thomas doing just that:

(Can't see the video? Watch it on YouTube or Youku).

Conclusion: Yes, air coming out of the purifier is clean.

2. Is the Smart Air DIY air purifier able to actually clean the air in the entire room?

Answering this question is more difficult because you need a controlled environment (for example, you don’t want to walk in and out of the room during the test), and you need to test the air for a longer period of time. But fortunately for you, Thomas is a huge nerd and does this kind of thing for fun.

To answer this, Thomas set up the particle counter on one side of his 13.5 m2 bedroom and put the DIY filter on the opposite side of the room. Here's what our filter did in one hour:


And over the course of eight hours:


The particle counter also gives data on .5 micron particles — even smaller than the 2.5 micron reading. Here's what that looks like over eight hours:


Conclusion: Yes, the clean air from the DIY filter is cleaning the entire room.

For fellow nerds, here are some more details on how the tests were conducted:

The test above was done starting at 11:30 pm on 6/16/2013, when the outside AQI in Beijing was 230 according to the US embassy's AQI Twitter feed. (The outside air improved the next day, but results were similar on a later test where AQI actually went up slightly from 195 to 202 during the test.)

According to comparisons of our particle counter's tests of outside to US embassy AQIs, an AQI of 230 would convert to about 2,650 on the PM 2.5 count on the reader. (Remember, the particle counter gives the raw number of particles 2.5 micrometers and above per .01 cubic feet. The US embassy takes mg/m3 and converts that to an AQI. Therefore, the raw numbers are different, but they correlate highly. You can think of this as the difference between measuring attendance at a basketball game by the number of people in the stadium versus the total weight of those people. The two numbers are highly correlated, but not identical.)

Thomas did the test in his bedroom with the doors and windows closed. The room is 13.5 m2, with two windows.

The particle counter tends to take 5-10 minutes to get stable readings, so to be conservative, Thomas gave it about an hour:


The spike at the top was when Thomas entered the room to turn the air purifier on and reset the machine, so it may be the dust he kicked up by walking around. A more stable reading for that time would probably be about 230.

The uptrend prior to turning the filter on may have been because Thomas was running a dehumidifier (which itself has some small filters) in the room before the tests.

Regardless, this data suggests that the effect of the filter was not a confound of calibration.

3. How well does the Smart Air DIY air purifier perform compared to expensive air purifiers?

Thanks to kind souls who donated a BlueAir 203/270E (3,600 RMB), a Philips AC4072 (3,000 RMB), and an IQAir Health Pro (8,000 RMB) we've finally been able to test the DIY against expensive brands in the same room, for the same amount of time, with the same particle counter.

To do that, Anna ran 11 overnight tests with the BlueAir, 9 tests with the Philips, and 11 tests with the IQAir. Thomas calculated effectiveness as percent reduction in particulates from the room air. Anna tested the air before she turned on the air filter, and then set the particle counter to take hourly measurements of the air in her 15 m2 Beijing bedroom. Anna used the highest setting on each filter.


All of the filters significantly reduced particulates, but the 470 RMB Cannon removed as many particles as the highest-performing big brand. Even the 200 RMB Original was only 6% behind the Blue Air on the .5 micron particles and 4% behind on the 2.5 micron particles.

Among the different brands, there seems to be no relationship between price and particulate removal:


Conclusion: You can remove particulate pollution from the air in your home and pay far less than the cost of a Blue Air, Philips, or IQAir.

For fellow nerds, here are more details on our data and methods:

Methods: Anna turned the purifier on the highest setting before she went to bed at night and turned it off after she woke up. To measure particulates, she used a Dylos particle counter, which measures particles .5 microns and above and 2.5 microns and above per .01 cubic foot. The particle counter took one measurement each hour.

Calculating Effectiveness: Thomas calculated effectiveness as the percentage of particles the purifier removed from the room air. The baseline was the particle count before turning on the purifier. The final count was the average number of particles over the last four hours before Anna woke up. We prefer this over comparisons to outside air because:

1. Indoor air is cleaner than outdoor air, even without a purifier (although that doesn't mean it's safe).

2. The baseline room number takes into account how dirty the outdoor air is because indoor particulates go up and down with outside air.

However, the drawback is that outdoor particulates sometimes go up after the test starts (lowering estimates of effectiveness) and sometimes go down (raising estimates). However, these average out over multiple tests, and the results are similar if you look only at days where outdoor particulates were relatively stable.

Room: Anna's bedroom is 15 m2, located in Chaoyangmen, Beijing. The doors and windows were closed while Anna slept, but she opened the door at various times in the very beginning of the test before she went to sleep. Although the doors and windows were closed, the apartment isn't new, and the seal isn't great.

For more details on the methods, see the end of Thomas's earlier post. All methods were identical to those earlier tests.

Machines: We tested an IQ Air Health Pro (8,000 RMB), Blue Air 203/270E (3,600 RMB), Philips AC4072 (3,000 RMB), Smart Air Original, and Cannon (Taobao).

Filter Life: After all the tests were done, the IQ Air said the pre-filter had 1,931 hours of use left, the carbon filter had 3,077 hours, and the HEPA had 1,910 hours. Thus, the filter was in its prime.

Data: Raw data for the Cannon, Blue Air, and Philips are in Thomas's previous post. Raw data for the IQ Air tests are below.

Outlier: Of the 11 tests, one day was a strong outlier. On May 22nd, the IQ Air got only 68% of the .5 micron particles. Normally when we see poor results, it's because the outdoor air got a lot dirtier during the night. But on May 22nd, the outdoor concentration fluctuated between 74 and 110 micrograms, which isn't out of the ordinary.

Because we couldn't see any reason the results were poor that night, we left the data in. If we redo the analysis with that day included, the results are only slightly better: 93.0% of .5 micron particles and 96.5% of the 2.5 micron particles. That would put the IQ Air about equal with the Philips and still 4% below the Cannon.







Have any questions about testing? Send us an email!
We're not PhDs in fluid dynamics, but we love to talk shop about clean air.

Frequently Asked Questions

No. Thomas, our data guru, is a PhD student in psychology at the University of Virginia. But we're firm believers in honest presentation of empirical data. Our philosophy is that no one should believe us just because we say so. Instead, we openly publish our data and methods so you can see how we reach our conclusions and judge for yourself. And we own a particle counter.

In our tests, our Cannon DIY outperformed a BlueAir and a Philips, so in a sense, yes! However, it's important to remember that these results are based on overnight particulate reductions in a 15 m2 bedroom, and don't take into account other room sizes or gas pollution (for example, carbon monoxide). But if particulate pollution is your primary concern (it's our main concern!) and your bedroom is 15 m2 or smaller (most are), then the DIY filters we sell perform about the same as (or in the Cannon's case, better than) the expensive brands.

You can! We have links on our Particle Counting blog. We're more committed to spreading the knowledge that HEPA filters are a cheap way to effectively combat air pollution than we are to making money, so we'd never discourage anyone from buying the same parts elsewhere.

We just try to make the parts easier to get for people who don't want to scour Taobao for the best filters. People have also emailed us saying that some stores stop carrying fans in the winter and that some HEPA manufacturers don’t sell in small orders. We buy in bulk so we can offer a low, flat rate (200RMB) that includes shipping anywhere in Mainland China. By buying with us, you also know that you’re getting HEPAs that we tested personally for effectiveness.

The pre-filter goes before the HEPA and filters out larger particles. This lets the HEPA focus on filtering out the smallest particles without getting clogged up by the big ones. We don’t include pre-filters on the Original DIY because the fan isn’t as strong as the Cannon. However, if you own the Original DIY and want to use a pre-filter, you can order them individually on our site.

We ship for free within Mainland China. We can also ship* to other countries by EMS or China Post for customers willing to pay for international shipping. We also offer cash-on-delivery for international shipping via SFExpress to Hong Kong, Taiwan, Macao, Japan, South Korea, Singapore, Vietnam, Thailand, Australia, and the US. Send us a message and we'll help you figure out the best shipping option.

If you're in India, we will soon be offering our DIY air purifier locally. Check out our India page and signup to be notified of our launch there.

*Shipping the actual fan (1.0 or Cannon) will be quite expensive compared to the price of the kits since the items are bulky but we can do that if you really want our fans. Our international customers usually get the filters and straps from us and use locally-sourced fans to save on high shipping charges.

Not tons. So far we're making enough to pay modest salaries to the people on the team, although Thomas is still working full-time for free. Any leftover cash goes to buying testing equipment and to development of our soon-to-be commercially produced affordable air purifier.

Yes. Tests show conclusively that the DIY purifier still cleans the room air (such as all 200 days of longevity test data here).

Big purifier companies have nice-sounding numbers for HEPA longevity--6 months! But what is that based on? And if a HEPA lasts 6 months in Sweden, will it last 6 months in Beijing? To get to the bottom of it, Gus tracked how much particulate his DIY Original removed in his Beijing apartment everyday for 200 days.

Results? In real Beijing air, effectiveness dropped significantly after about 140 days (almost 5 months) at 8 hours a day or about 1,000 hours total. So we suggest changing your filter before this. See the full results and method here.

Remember that this result may not hold for the Cannon. So now we're doing a Cannon longevity test!

Thomas tested this by setting a Cannon to turn on and off automatically in an empty room over the course of six days, and recorded how quickly particulates rose and fell. On average, the Cannon cut .5 micron particulates in half in 10 minutes. By 20 minutes, it removed 80%. That's pretty fast, so unless you have noticeable symptoms there's no need to leave it running while you're not at home. It's fine to turn the purifier on when you get home. See the full results and method here.

Even in a room with the doors and windows closed, our tests found that particulate levels increased very quickly after the purifier was turned off. Dirty air is entering our homes constantly, even though we can’t see it. That's why we don't recommend turning the purifier off while you sleep. See the full results and method here.

Don't see your question answered? Get in touch and we'll get back to you as soon as we can.

Who are we?

Smart Air is a small social enterprise that promotes DIY air filters as a low-cost solution to indoor particulate air pollution in China.

In January 2013, PhD student Thomas Talhelm wondered why air purifiers cost so much. He bought a HEPA filter on Taobao, strapped it to a simple fan, bought a particle counter, ran some tests, and published the results on a blog he called Particle Counting.

A few magazines wrote about Thomas's "re­discovery," and then the Beijing Energy Network suggested he lead DIY workshops to help other concerned Beijingers build their own.

When people said they had trouble finding the right type of fan and a trustworthy HEPA, Thomas and his friends Gus and Anna decided to launch Smart Air in September 2013 to ship fans and the best HEPAs they could find to people all over China.

Smart Air believes that if more people saw our open­source data and testing, more people would know that clean air doesn't have to cost thousands of RMB.

The Smart Air Team

Clockwise: Noah, Thomas, Matt, Anna

The Smart Air China Team


Thomas Talhelm

Thomas built his first DIY in Beijing doing PhD research in cultural psychology. Since then, he somehow managed to get a job as a professor at the University of Chicago. When he’s not leading Smart Air, Thomas studies cultural differences between northern and southern China.


Anna Guo

Anna helped Thomas assemble his first DIY air filter in 2013 and has been tolerating his incessant particle counting ever since. Now she runs tests, orders materials, and manages team projects for Smart Air. In her spare time, Anna enjoys photography, yoga, tea, and French film.


Paddy Robertson

Recently moved to Beijing, Paddy is a graduate in aero engineering and a trick of several trades, having started his own company in the UK. Paddy joined Smart Air in 2015 after deciding to put his engineering skills to good use. He manages the China business and leads product development. When not at work you'll find Paddy climbing or trying (and failing!) to fit in with the locals doing Tai Chi.


Esther Wang

Esther is Smart Air China's customer service lead and prior to the recent epidemic of babies in her life, she enjoyed music, dancing, traveling, and ultimate frisbee. And she hopes to enjoy them again someday.


Noah Willingham

Noah bases his China adventures out of the lovely city of Hangzhou. He is helping Smart Air put on workshops throughout the Yangtze River Delta.


Aily Zhang

Originally from San Francisco, Aily is now based in the Beij and runs bilingual workshops for Smart Air across Northern China. She also assists with business development projects. While not giving talks on health interventions for air pollution, Aily can be found with her nose in a book, chowing down at a 饺子馆儿 jiaoziguanr, and going on runs (to compensate for pigging out on tons of vegetarian dumplings #Itis).

Questions, comments, complaints? Send us a message at info@smartairfilters.com

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