What is the best air purifier on the market today?

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 the very small particles of smog, mostly 2.5 microns and below. Can air purifiers get particles that small?

 

 

I saw air purifier tests done by a doctor in his own apartment in Beijing (Richard Saint Cyr MD). 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

I’ve tested several big brand purifiers in my apartment in Beijing, including that fancy IQ Air above.

 

 

Averaging over dozens of tests, I found no correlation between price and effectiveness.

 

 

(All of the data and methods are publicly available. I also published instructions for making your own purifier.)

2. Another Citizen Scientist’s Home Tests

Another dedicated nerd with very fancy test equipment published tests of several big brand and less-big brand air purifiers 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 the tests of the Shanghai Consumer Protection Bureau. 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:

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 DIYs!) 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.

 

 

Studies show they are not effective in the doses seen in most commercial machines, and they create ozone. I wrote a simple explanation of how ionizers work here. (Also check out Consumer Reports’ warning against ionizers.)

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 says: recommends to “avoid dedicated ozone generators entirely.”

Breathe safe!

 

The Sqair air purifier Kickstarter

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carlealexis

Dear Thomas,

DO you think it’s effective to put HEPA filters on apartment Air Con?

Thank you for your help

Great question @carlealexis! I’ll answer on behalf of Tom, since I ran some tests from our Beijing lab to test this. There are single sheets of filter material which you can place on air purifiers. What we found was that they do have a measurable effect on reducing indoor PM2.5 levels, but it’s not enough to bring levels right down to safe levels. One thing we did find is that doing this may reduce the ability of the Aircon to lower your indoor room temperature. We’ll have a writeup on this soon!

suppathanis

How about installing HEPA car air filters, is it effective? Using a car air purifier is enough or not? Will HEPA car air filter help make it any better or it’s unnecessary?
Please also review car air purifiers in the maket.

Hi Meow! We’ve actually tested car HEPA filters, and there’s some good news – you don’t need them! Read up on whether we really need car air purifiers. Short story: our cars already have powerful air purifiers built in (the AC system). Make sure to run that on high and in re-circulate mode and you should get clean air in your car!