Last January we had the airpocalypse, and this January — hell hath frozen over. Because a bright-eyed Fulbright scholar and his disciples are spreading across China, preaching in their revival tents to swooning crowds that “you — yes, YOU, ma’am, in the corner!” (rising applause) “Yes, I swear to you right now that you can make your own air purifier for under 200 RMB — and get the same results as your fancy-schmancy, Perrier-sipping import! Can I hear a yee-haw!” (wild clapping).
I refer to Thomas Talhelm’s evangelistic, data-filled blog and his company spinoff, Smart Air Filters, offering frequent DIY workshops on just this subject, as well as selling their own two models. And yes, the cheaper one is really only 200 RMB. Crazy, no? Like a fox, maybe. Because Thomas’ scrupulous data, far geekier than anything I’ve written (that’s a compliment), does indeed show quite impressive PM2.5 reduction with these machines, even when directly compared to some famous models we all know about.
Thomas actually was inspired to do his own testing from all of my own tests and blog posts, and we’ve been emailing back and forth since last summer, comparing notes. As I mentioned last week in my Philips review, I’m quite a fan of his goal to find affordable protection for the masses against indoor air pollution. And his message has spread quickly, with many news groups covering the story. Many of my readers have asked me to review his machines, and I recently got to test both his Original and Cannon. So how did they do? Is he a prophet or a charlatan?
Let’s cut to the chase: a true HEPA filter and a strong fan indeed are all you need to eliminate bad particles in the air. Almost every top air purifier machine out there, no matter how fancy, is still built around those two pieces: a HEPA filter rated to eliminate 99% of particles larger than PM0.3, and a fan blowing air through it at a proper flow rate. No other features really matter as much as this, at least here in China. If you have a car, a HEPA filter can go into your exhaust system and clean your air; if your home or office has an HVAC system, installing a top-rated HEPA filter is incredibly effective, and much cheaper than a floor machine.
So yes, it makes perfect sense that a do-it-yourself combo could work — and it does. I tested the smaller Original model in my three small rooms, 10-13 square meters in size, overnight with the doors closed. And this little guy did about as well as any other machine I’ve tested: PM1 levels were 91% lower than the outdoor air, and PM5 levels were 95% better. This was on its lowest speed setting, which was tolerably loud but certainly noisier than my usual Blueair settings at night. In my most recent testing of Blueair, IQAir and Airgle, I got bedroom results of 88-90%. For small rooms, this little HEPA filter was at least as efficient as all of the big boys.
Thomas tests his machines a bit differently than I do, comparing them to the same room before and after, and he also measures PM0.5 and 2.5, whereas my Dylos machine measures PM1 and 5. He also mostly tests on highest fan speed, which I find impractical and too noisy for a real world scenario. But even with these differences, we still got about the same results: effectiveness always at least in the high 80%, which also at the very least was a strong match to the bigger machines — sometimes better.
So our data does match, and again why wouldn’t it? He’s using a real HEPA filter and a fan with a flow rate that works. I think their smaller Original model is especially a reasonable option for students and people with limited income to use in their bedrooms. It certainly is far, far better than having nothing at all, when the AQI outside is crazy bad.
His newer machine, the 450 RMB Cannon, was designed for bigger rooms, and I think that also could work well in theory, since it’s the same HEPA filter on a stronger fan. I wish I could share hard data with you, but honestly I didn’t get a lot of data points on this machine, mostly because it was just so darn noisy that I didn’t want to test it any more in my living room. Even at the lowest setting overnight, it was much louder than normal background decibels from my current IQAirs. For me at least, that’s a non-starter as an option. Thomas openly admits that the Cannon is a bit loud, but it still is effective even on low settings (see the graphic to the right).
But let’s not get bogged down in the details of these two models. These are early, first generation attempts, and besides, it’s distracting from his and my main message: everyone everywhere should always try to limit their exposure to pollution, and a DIY HEPA filter and fan combo are a heck of a lot better than nothing at all.
I assume the PR teams at the famous air purifier headquarters are now champing at the bit to correct me, aghast that I would gloss over their superior technology. And of course that’s partly true, as some top end filters do indeed claim to filter down to PM0.003, a hundred times smaller than a normal HEPA. Not to mention the other filters for VOCs and other chemicals besides PM. And maybe that does matter in a place as polluted as China — but I haven’t seen any data or medical resource claiming any specific advantage in targeting those ultrafine particles. Perhaps in the next couple years, with better research, we may learn that spending that extra $$ on the top end models may prove more beneficial to your health.
Until then, I say to the hundreds of thousands of people who’ve bought air purifiers: keep up the good work. But for the hundreds of millions of unprotected people across the developing world, anxiously awaiting the next inevitable airpocalypse — go get a HEPA filter and stick it to a fan. And buy yourself a particle monitor, test your machine, and blog about it. Viva la consumer revolution!
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