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Xiaomi Smart Air Purifier 4 Compact review: cheap and effective

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At first sight

Expert assessment


Solid performance for the price Simple and easy setup Lots of in-app options


Minimal built-in controls, including no true manual mode No countdown timer, no logging Uses proprietary air filter, rather than HEPA

Our verdict

This is a largely generic purifier designed for small spaces, but its smart features work well and it’s priced to move.

Price at time of review


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You’ve seen this product before, I’m sure, or at least something nearly identical to it. It’s a compact, no-nonsense purifier that’s easy to move wherever you need it. So what makes it different?

Xiaomi makes a range of larger air purifiers, with this member of its Compact line designed for smaller spaces. The cylindrical, all-white device is just 14 inches tall by 9 inches wide and weighs just under 5 pounds. A cylindrical filter (which runs through the bottom of the purifier) ​​is not a HEPA filter but rather a proprietary filter made with “electrostatic technology melt-blown PP fibers” instead of the usual glass fiber used in HEPA designs.

This review is part of TechHive’s in-depth coverage of the best smart air purifiers.

A “Smart Scenes” feature lets you set up multi-device automations if you have more than one compatible piece of equipment

origin 1Like us, you are probably very familiar with HEPA air filters, which leaves us wondering why Xiaomi had to come up with its own standard.

Christopher Null/Foundry

Xiaomi claims its filter performs better than HEPA, and while I’m not sure if that claim is easily verifiable, Xiaomi’s claimed specs are roughly on par with those of similarly powered HEPA-based purifiers. Specifically, the company claims a CADR (clean air delivery rate) of 135 cubic feet per minute for particulate matter (no failures beyond that) and boasts a maximum coverage area of ​​516 square feet. That’s an impressive CADR given the small size of the device.

Operationally, the device is very simple, with air drawn in from the base and emitted upwards through the top. A control panel is centrally mounted on the top panel, with three basic functions: power, a button for dimming, and a button that allows you to toggle between auto, sleep, and manual modes. You cannot change the manual mode power on the device itself; for that, you’ll need to use the Mi Home mobile app, where a slider lets you adjust the fan speed to your liking. The button on the hardware itself simply selects the most recent speed you’ve selected within the app.

origin 1A simple set of touch controls is available on top of the Xiaomi Smart Air Purifier 4 Compact.

Christopher Null/Foundry

The purifier hardware also includes an additional feature: a color-coded air quality indicator that can display one of four levels of PM2.5 concentration, ranging from green (best, less than 35ppm) to red ( worst, more than 150 ppm) . Filters are rated to last 6 to 12 months; replacement costs have not yet been announced.

Connecting the Xiaomi purifier to your home network is easy. The Mi Home app automatically detects the device via Bluetooth, then quickly connects it to the 2.4GHz Wi-Fi network. As noted above, the app offers more detailed manual controls, as well as a collection of additional features, including a child lock, a simple scheduling feature, and a more complex “Smart Scenes” feature that lets you set up multi-device automations if you have more than one compatible piece of equipment.

origin 1The Xiaomi Smart Air Purifier 4 Compact app makes it easy to integrate into the typical smart home environment.

Christopher Null/Foundry

This IFTTT-like system lets you connect equipment to each other however you like; for example, turning on a light when the purifier is running. You can also schedule automations, but for most people the standard scheduling option should be sufficient. Curiously, there is no countdown timer in the app, nor is there any long-term recording functionality. You can, however, connect the device to Alexa or Google Home, allowing for further changes.

At full speed, the Xiaomi purifier is loud but not deafening at all, and anywhere less than half power or below is largely inaudible. Better still, with a street price of around $100, this is one of the most affordable purifiers on the market, particularly among those with clever features. While I can’t comment on how effective its proprietary filter is in relation to a real HEPA filter, at least it appears to be effective, and its specs are impressive. While claims to be “better than HEPA” are always a little fishy, ​​I have no reason to believe this device doesn’t perform at least as well as one.