N95 versus KN95 Mask Difference Standards

What’s the Difference Between N95 and KN95 Masks?

With such similar-sounding names, it can be confusing to understand the difference between N95 and KN95 masks. What are KN95 masks, and are they the same as N95 masks? This handy chart explains the differences between N95 and KN95 masks (and all characteristics that are the same). N95 vs. KN95 … Read more

how to choose best air filter air purifier guide

Four Steps To Choosing The Best Air Purifier

“What’s the best air purifier on the market?” It’s a question that many of us might ask. There are thousands of air purifier models to choose from, so how can you find the best air purifier that’s right for you? This article covers those steps in a slightly unorthodox way. What’s … Read more

Did China’s Air Quality Improve in 2019?

After a big improvement in 2018, new data shows China’s war on air pollution is slowing down. A Smart Air analysis of 2019 PM2.5 data for China’s 15 largest cities found that more than half saw worse air quality over 2018. Maps comparing average PM2.5 in December 2018 to December 2019 … Read more

DIY air purifier effectiveness blueair iqair philipps cheap god air purifier

Directly Comparable Tests: DIY vs Blue Air

I’ve wanted to know for a long time whether DIY air purifiers are as effective as the Ferrari filters.

DIY Air Purifier Cheap

In an earlier post, I compared my data to the tests of Dr. Saint Cyr (whose excellent posts inspired me to look into filters in the first place). But I noted that the comparisons were far from perfect because:

  1. The rooms were different.
  2. The Cyr post did not specify how long the tests were (and that can make a big difference if you’re looking at times under an hour–see this time comparison).
  3. The Cyr post did not describe the particle counter or particle size.

How We Tested The Air Purifiers

But now I finally have directly comparable data! That’s because two kind souls donated a Blue Air 203/270E (3,600 RMB) and a Philips AC4072 (3, 000 RMB). That means I could finally test the DIY against expensive brands in the same room, for the same amount of time, with the same particle counter.

DIY Purifier Test Method PM2.5

To do that, Anna ran 11 overnight tests with the Blue Air and 9 tests with the Philips. As always, I 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 a Dylos DC1700 laser particle counter to take hourly measurements of the air in her 15m2 room.

DIY Air Purifier PM2.5 Test

Anna used the highest setting on each purifier. (I’m putting the original data and more details about the methods for fellow nerds at the end of this post.)

And (drumroll!) here are the results:

DIY Purifier Test BlueAir Philips IQ Air PM2.5

The Cannon removed as much particulate as the expensive machines. Not bad for 450 RMB!

Yet all four filters were making the room air significantly cleaner. For particles 2.5 microns and above, all four removed over 90%. For particles 0.5 microns and bigger, all four removed over 80%. I’m not the first person to say: All you need to significantly reduce the particulate pollution in your home is a simple HEPA filter.

Based on the data, here’s how much you’re paying for each percentage reduction in 0.5 micron particles:

Price versus Effectiveness DIY Air Purifier Philips Blueair

(And that’s not counting the cost of the exorbitantly priced replacement filters.)

Recently, a Chinese news article claimed air filter companies are making “falsely inflated profits.” That fits with this data showing that the Cannon removes as much particulate as the Blueair, yet costs about 10% per percentage of 0.5 micron reduction. Similarly, the Original DIY removes 4% less 2.5 micron particulate and 6% less 0.5 micron particulate than the Blueair on average, yet the Blue Air costs more than 16 times as much.

Bottom Line: Air Purifier Test

You can remove particulate pollution from the air in your home and pay far less than a Blueair or Philips

Smart Air

What About Gas Pollution?

Now, as I’ve said before, particulates are not everything. There are also gases like ozone and nitrogen dioxide (although I’m less concerned about those). Here’s how to know whether your home has serious gas pollution. If it does, tests show that activated carbon removes gases like formaldehyde and benzene.

Open Data and Methods

As always, I’m posting the original data and detailed methods for fellow nerds. Don’t believe me. Check out the data and decide for yourself.

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Are Particle Counters and Government Machines the Same?

My particle counter is a beast–I’ve loved it. But I’ve always wondered how the counts of laser particle counters like mine:     …compare to the measurements of the huge stationary air quality monitoring stations that governments use, like this one in New Zealand:     If you look at … Read more

Comparing Air Purifiers

Dr. Saint Cyr recently pointed me to great tests of air purifiers from the Shanghai Consumer Protection Bureau: The reason this type of research is so badly needed is that Western research (like this report from Consumer Reports) focuses on allergens, not general industrial air pollution. Allergens are probably more … Read more

Smart Air is a social enterprise that creates simple, no-nonsense air purifiers and provides free education to protect people’s health from the effects of air pollution. We are proud to be the only certified B-Corp dedicated to fighting air pollution.