I started thinking about this question a lot because I was living in Beijing, and the “airpocalypse” struck:
I had a cough I couldn’t shake for weeks, so I started doing research into air purifiers. Unlike another answer here, I wasn’t concerned about allergens like pollen. I was concerned about , mostly 2.5 microns and below. Can air purifiers get particles that small?
I saw air purifier tests done by (). He used a laser particle counter to test his home for the very small particles that can penetrate deep into our lungs.
His results were straightforward: the purifiers he tested reduced the particulate in his home.
So I went out to buy one of the purifiers he tested, and wham!
That leads me to how I answered this question as an air-breather in a polluted city. When I was searching for purifiers, I found lots of pages saying that you need to spend a fortune to get clean air. Or some say, “Sure, this cheap thing works, but don’t you want the best!?”
I’m not going to point to a single brand, but I’ll talk about air purifier test data from multiple sources that leads to a conclusion:
You don’t need to spend a fortune to protect yourself from air pollution. Some of the best-performing machines are also the cheapest.
1. My Tests in Beijing
in my apartment in Beijing, including that fancy IQ Air above.
Averaging over dozens of tests, I found no correlation between price and effectiveness.
( I also published .)
2. Another Citizen Scientist’s Home Tests
Another dedicated nerd with very fancy test equipment published in the US (the original report keeps changing–and oddly removing test details–so I archived the early version as a resource for all, also available on the Internet Wayback Machine).
Here’s what he found:
His tests similarly found that the most expensive purifiers were not always the best. The most expensive purifier was actually second to last in his test.
3. Shanghai Consumer Protection Bureau Air Purifier Tests
Perhaps an even more extreme test of this idea are . These air purifier tests might be more extreme because they tested many machines made in China for the Chinese market, and China is not known for high-quality products. Thus, if we were to expect crappy, low-price machines to fail, here’s where we should find it. But here’s what they found:
Notice that the Sharp and Electrolux were among the cheapest machines, but they removed as much particulate as brands that cost more than twice as much.
(Nerd note: these air purifier tests use different methods. For example, the tests in #2 and #3 burn source of pollution in the room. My air purifier tests and the doctor’s tests use naturally occurring air pollution in Chinese apartments. That means we can’t translate percentages in one test to another test; instead, we should compare price and effectiveness within each test.)
4. Other tests
Results are similar from other third-party tests of purifiers, such as:
- (results behind a pay wall)
Conclusion: How to choose a purifier
All of this test data points to three simple conclusions:
1. We don’t need to buy the most expensive machines to get clean air.
2. There are many options on the cheap end of the scale (including !) that remove as much particulate as the big boys.
3. Choosing a purifier is as simple as checking out the empirical data linked above and selecting the best combination of effectiveness and price.
After I did all of these tests and read other people’s tests, I now use simple DIY purifiers in my apartment in Beijing. I know several people who have paid for that 14,000 RMB ($2,138) IQ Air I first read about; in my home, I’m protecting my lungs for and paying about 3% of that price.
Two More Tips
1. Avoid ionizers.
they are not effective in the doses seen in most commercial machines, and they create ozone. I wrote a simple explanation of here. (Also check out .)
2. Avoid ozone generators, unless you’re not planning on being in the room.
Ozone can clean the air, but it’s harmful to humans. To give a sloppy analogy, it’s kind of like filling your home with landmines to protect against intruders. They’d kill intruders, but also us! Consumer Reports recommends to “avoid dedicated ozone generators entirely.”
Thomas is an Associate Professor of Behavior Science at the University of Chicago Booth School of Business and the founder of, a social enterprise to help people in China breathe clean air without shelling out thousands of dollars for expensive purifiers.