Mi Air Purifier 2S: new OLED display makes it a winner, and laser sensor to respond better to bad air a great addition

Upgrades to Xiaomi device, including display of air pollution, humidity and temperature in app and on the purifier, make it a worthwhile addition to any household

PUBLISHED : Saturday, 12 May, 2018, 8:02pm
UPDATED : Sunday, 13 May, 2018, 8:25pm

There are many air purifier on the market right now, but most are pricey. That’s why the Mi Air Purifier 2S may appeal to those on a budget, with an agreeable price tag of HK$849 (US$108).

Hardware and set-up

The Mi Air Purifier 2S is the latest iteration of air purifiers from Xiaomi, the smartphone company that in recent years has expanded into producing a range of consumer electronics, including smart home devices. Unsurprisingly, the Air Purifier 2S packs a dose of smarts you don’t see in most competitors, such as Wi-fi connectivity and remote management from the Mi Home app.

The white device adopts the design language of its predecessors, with a tried and tested tower structure for a compact footprint that should fit well in most households.

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Visually, one key difference over the earlier non-“S” model is the addition of an OLED display to show key data such as the current PM2.5 reading (a measurement of fine particle concentration that is one of the determinants of air quality). In addition, the company says it drilled 943 more intake holes to increase air intake and circulate air better.

Setting up the device is a simple matter of taking it out of the box and plugging in the power cord. A replaceable air filter is already fitted. You will need to download the free Mi Home app to configure the air purifier. Simply detect and add the Air Purifier 2S from the app, select the right Wi-fi network and key in the passphrase, and you are good to go.


One of the primary selling points of Xiaomi’s family of air purifiers is their ability to automatically respond to the quality of the air by adjusting the fan speed: the higher the speed, the more air is forced through the filter; dust and other PM2.5 nasties get filtered out as a result.

This feature gets a performance boost in the Air Purifier 2S with the inclusion of a high-precision laser sensor, which relies on the scattering of laser irradiation to more accurately determine the presence of particles in the air.

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While the device operates in auto mode by default, you can adjust the fan speed manually by tapping on the “Manual” button in the Mi Home app and adjusting the slider. The fan is typically whisper-quiet, but it can get plenty loud when you dial up the settings.

At maximum speed, the Air Purifier 2S is noticeably louder than an air conditioner with its fan on high setting, though room coverage also goes up in tandem.

If you are sensitive to noise, a night mode is available that throttles the fan all the way down just to keep the air flowing. This can be activated either from the app, or by tapping on the physical power button once.

Speaking of nighttime use, a built-in light sensor automatically dims the brightness of the OLED display in the evening; you can also switch the display off entirely by tapping on the display button on the back of the device.

Software and features

It is easy to see that the Air Purifier 2S is designed to be kept switched on the entire day, spinning up automatically when it senses pollution and back to low-speed operation when the air improves. The fan never stops spinning unless you power the device down, though leaving it on probably won’t affect your power bill too much. Xiaomi says the custom-made motor draws a mere 4.8 watts in normal operation, which is less than a typical energy-saving light bulb.

What I really liked was the ability to view the current PM2.5 reading, temperature and humidity from both the Mi Home app and the physical OLED display.

Xiaomi has also made it easy to change the three-in-one air filter, a cylindrical cartridge that can be easily removed by opening the back panel. You can choose one of three different filters: a standard one, one imbued with additional properties to remove formaldehyde from the air – great when moving into a newly renovated place – and a third option that is designed for superior trapping of bacterial nasties.

I personally didn’t like the fact that there doesn’t seem to be an easy way to clean the internal fan, but considering that it is located after the filter and designed to blow air upwards, a dusty fan is probably a sign you are skimping on changing the air filters. Xiaomi says they should be replaced every six months, and the app helpfully shows an estimate of how much of the filter’s lifespan remains.

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It is arguable that the Mi Air Purifier 2S offers an incremental update that won’t entice existing customers; it certainly does nothing to rock the boat in terms of its core design and capabilities.

Yet there is also no question that the addition of an OLED display with easy-to-understand readings significantly increases its user-friendliness, while the new laser sensor makes it a highly compelling device for those looking to get a second or third air purifier for their homes.