Xiaomi 2 Air Purifier Auto Mode Leaves Air Unsafe For 86% Of The Time


Ever since I coughed through a Beijing airpocalypse, I’ve sầu been saying clean air doesn’t need khổng lồ cost an arm và a leg. I even set up Smart Air to provide low-cost purifiers khổng lồ people around the world based on that data.

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So when the Xiaomày 2 air purifier came out for under $150 (10,000INR / 1,000RMB), I assumed it works just fine. But I had never gotten around to lớn testing it—until now. And what I found testing the Xiaomi Mi 2 shocked me.

Xiaomi Mi 2 Air Purifier: Put To the Test

Smart Air co-founder Anmãng cầu ran a brand new Xiaongươi Mi 2 air purifier in the 15mét vuông Smart Air thử nghiệm bedroom where we’ve sầu tested the DIYs, IQ Air, Blue Air, and Philips. Anna ran six tests on tự động hóa mode & six tests on the highest setting (which the Xiaongươi 2 air purifier oddly calls “Favorite mode”).


Anna turned the purifier on in the morning when she left trang chính, và turned it off when she returned trang chính. That means there was no one in the home during the tests. The doors và windows were closed during the tests. (More details on the demo method & all original data are here.)

A Dylos Pro tracked ≥ 0.5 micron and ≥ 2.5 micron particle counts during the demo. Test data shows these 0.5 micron readings correlate highly with the US Embassy’s PM2.5 readings (r = .90).

As in my earlier tests, I calculated effectiveness as (the number of particles before turning the purifier on) versus (the average number of particles over the last four hours).

Xiaongươi 2 Air Purifier Test Results

The Xiaomi purifier scored as one of the worst purifiers I’ve sầu ever reviewed. On average, it removed only about 60% of 0.5 micron particles over the last 4 hours of the demo.


And oddly enough, the tự động hóa mode và the high mode results of the Mi 2 purifier were nearly identical. That’s a mystery.

Here’s how the Xiaomi results compare to lớn earlier results from other purifiers using the same method, same particle counter, in the same room.


The data shows the Xiaomày air purifier performed worse than the $30 DIY purifier I’ve been showing people how to make for years!

Below is a normal chạy thử day. I put a dashed red line representing the World Health Organization’s 24-hour PM2.5 limit (25 micrograms).


The Xiaongươi Mi Air Purifier Really Wants To Be in Auto lớn Mode

What’s wrong? The key is that—even on the highest setting—the Xiaomày reverts baông chồng lớn tự động hóa mode after 3 hours..

WATCH: Xiaongươi Reverts lớn Aulớn Mode After 3 Hours


You can see the noise remaining high for three hours, then it returns khổng lồ the ups and downs of auto mode:


Here is the same graph with particle counts (measured by the Dylos). The particle counts rise sharply every time the machine turns off.

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The data shows that Xiaomi has a loose standard for “safe.” The Xiaongươi is turning off when PM2.5 reaches 40 micrograms, which is far higher than even the WHO’s 24 hour limit. And it’s far higher than levels where we know PM2.5 has serious health effects from empirical retìm kiếm. Then it turns on again when PM2.5 gets up khổng lồ 70 micrograms—almost three times the limit.

Really? The Xiaongươi air purifier won’t stay on high?

The fact that the Xiaongươi air purifier can’t be kept on continuously all night is so strange that Anna asked Xiaomày customer service over at ngươi.com. She asked twice to make sure we’re not making a mistake. They confirmed that, no matter what, the machine will go back lớn auto mode after three hours. (full transcript available in the supplemental materials).


How often is the air unsafe with a Mi Air Purifier?

I calculated the percent of hours that the air was unsafe for the Mi air purifier during the tests using this rule:

After the purifier was on for at least 1 hour, for any hour where outdoor air pollution was unsafe (> 25 micrograms – the WHO 24-hour limit), how many hours was indoor air also unsafe (>25 micrograms)?

The Xiaomày Mi air purifier left air unsafe for a shocking 86% of the time. The other similarly sized machines in my earlier tests left air unsafe only 7-16% of the time.


Maybe the Xiaongươi Mi2’s tự động mode is using the looser Chinese standard for clean air of 35 micrograms. Yet even with that high number, it was still above the limit 77% of the hours the Xiaongươi Mi2 was running.

Learn More: we subsequently ran tests on the particle counter inside the Xiaomày Mi2, và what we found was shocking ».

Wait, are you sure?

I wanted khổng lồ be really careful about this Reviews. I’ve seen other tests showing that the Xiaongươi 1 air purifier works just fine, including these tests from Dr. Saint Cyr (although I’ve sầu seen people write about flaws too, such as this guy who kept the filters wrapped in plastic, turned it on turbo mode, và the tiện ích told hyên his air got miraculously cleaner). So I double & tripled checked the data:

We tested with a different particle counter in a different room.I re-analyzed the data throwing out any days with large fluctuations in outdoor air.I analyzed days when outdoor pollution was low to lớn average (I compared it lớn other tests done just two weeks before in the exact same room with the exact same particle counter.

None of these analyses changed the result (see details here).

Bottom Line: Performances of Xiaomày Mi2

From this data, my conclusion is that the người và the filter are fine, but the Xiaongươi air purifier has a programming flaw. Even if I use it on the highest setting, I’ll be breathing air far above the safe limit for most of the night. That’s a problem.

Is it just a Xiaomày Purifier Problem?

To be fair, I cannot recommkết thúc any tự động mode I’ve sầu tested. I’ve sầu tested the Philips AC4072 on auto mode, & it averaged 59% reductions in 0.5 micron particles, which is pretty cthảm bại to the Xiaomi results. So I think this is more of a problem with tự động hóa modes rather than the Xiaomi specifically.


Yet I can still recommover the Philips. Why? It can stay in medium or high as long as you want, & demo data shows it works fine all night as long as it’s not on auto mode.

I’m confident that Xiaomi can fix this flaw by simply allowing people khổng lồ run it on high without reverting back khổng lồ auto mode. But until that happens, I cannot recommkết thúc using the Mi2.

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Open Data

As always, I’m publishing more details on the kiểm tra method and the original data for fellow nerds.

nhận xét Update: July 2018Some users have sầu reported that they are able khổng lồ get their Xiaomi air purifier khổng lồ remain in ‘high’ mode using the ‘automation’ feature of the ứng dụng. For more information, kiểm tra out this comment by Ryan, and this image showing how khổng lồ mix up tự động mode. Breathe safe!