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Xiaomi Smart Air Purifier Pro 4 Review: 11 Objective Tests

Derek Hales

Written By: Derek Hales

Updated on:

Xiaomi Pro 4
91 Purification
91 Build Quality
95 Noise
92 Usability
96 Maintenance
92.0 Overall Score
Tested With Scoring System 1.1

Best For

  • Great purification performance, reduce PM2.5 to 0.3 within 2 hours
  • Touch display and app connectivity
  • Auto and sleep mode


  • Tall air purifier, isn’t easy to move around
  • Small coverage area compared to the size of the system.

Our Verdict

The Xiaomi Smart Air Purifier Pro 4 has a modern design with great usability features. It has an auto mode which adjusts based off of readings from the internal sensor and a sleep mode for silent air purification. The Pro 4 was able to remove 97.6% of particles in our tests and reduce the PM2.5 to 0.4. This solid performance is coupled with great features, which would be a great fit for any home.

Filter Type: Pre-Filter, Proprietary (non-HEPA) filter, Activated Carbon, Negative Ion Filter
Coverage Area: 645 sq. ft.

In This Review
Purification Performance | Ozone Test | Filters | Coverage | Build Quality | Noise Test | Usability | Maintenance | Size | Specs | Product Evolution | Comparison | FAQs

Performance Summary

At Modern Castle we test 11 different factors that impact the performance, build quality, and usability of the air purifier. Below is a complete list of our testing categories and their performance.

Test TypeTest Data
PM2.5 (2 hour test)0.3 ppm
PM10 (2 hour test)0.4 ppm
Particles (2 hour test)59
AQI (2 hour test)1
Ozone Detected0.0 ppm
Filter TypeCarbon, Pre-Filter, Ionizer
Coverage Area646 sq. ft. (60 sq. m.)
Max Wind Speed12.1 mph (19.5 kph)
Noise Test57.8 dB

Purification Performance

To test the purification performance of the Xiaomi Smart Pro 4, we placed it in a medium-sized room in our office (~14’ x 10`). Next, we lit incense to introduce smoke and other particulates into the air for 30 seconds. After, we use a professional air quality detector to take a measurement of the smoke filled air.

Air Quality Testing Meter
Electronic testing meter we use to measure particulates and air quality

Next, we run the air purifier on the highest fan speed for 2 hours, taking measurements of the air quality at the one hour mark and the end of the test. Here is what we found:

Performance MetricStarting MeasurementAfter 1 HourAfter 2 Hours
PM2.524.8 ppm0.4 ppm0.3 ppm
PM1043.5 ppm0.6 ppm0.4 ppm

The Xiaomi Smart Pro 4 showcased good results reducing PM2.5 down to 0.3 and PM10 down to 0.4 after the 2 hour test. By comparison the average air purifier we test is able to reduce PM2.5 down to 0.2 and PM10 to 0.3. The Smart Pro 4 had slightly worse performance, but still within healthy breathing levels.

Xiaomi Smart Air Purifier Pro 4
Xiaomi Smart Air Purifier Pro 4

Below, we’ve included information on the testing criteria and what defines good vs. bad air quality. Simply, the lower the numbers the better.

Air Quality Pm 25 Index

This is somewhat surprising considering the 1 hour test results. After 1 hour, the Smart Pro 4 reduced PM2.5 to 0.4, only 0.1 more than the 2 hour test results. Still, both the 1 hour and 2 hour results are well with healthy breathing levels.

Ozone Test

With most air purifiers ozone generation isn’t an issue. That said, some that use negative ion generators have the potential to create ozone. To test this, we run the Xiaomi Smart Air Purifier Pro 4, letting it run for 1 hour and measure the levels of ozone before and after with an ozone meter device.

Pre-test Ozone

0.0 ppm

Post-test Ozone

0.0 ppm

In our ozone tests, the Xiaomi Smart Air Purifier Pro 4 generated 0 ppm. This is consistent with all air purifiers we have tested to date.



The Xiaomi Smart Pro 4 comes with 3 different air filters and an always on negative air ionizer.

Xiaomi Smart Air Purifier Pro 4 filter

Proprietary Non-HEPA Filter – The filter does the majority of the work capturing particles as small as 0.3 microns. Notably, the filter is not a HEPA filter. It is a proprietary design.

Xiaomi Smart Air Purifier Pro 4 filter

Activated Carbon – These filters focus on capturing VOCs, odors, and gasses that the pre-filter and the HEPA filter miss.

Xiaomi Smart Air Purifier Pro 4 filter cover

Pre-filter – These air filters are designed to catch larger particulates in the air before the main filters. It’s best designed to catch human/animal hair, lint, or large dust particles.

Xiaomi Pro 4 Hero

Ionizer – This feature releases negatively charged particles into your environment, forcing extremely small airborne particles to clump together and fall to the floor. This feature can be turned on or off.


The Xiaomi Smart Air Purifier Pro 4 has a coverage area of 645 sq. ft. It is best suited for small to medium sized homes.

Coverage Area

646 sq. ft.


500 CFM

For the size of this air purifier, we would expect the coverage to be higher than just 646 sq. ft. Compared to some of the other full sized models we have tested, they typically get closer to the 1000 sq. ft. and above. The Pro 4 was 80.6 sq. ft. below our coverage testing area of 726.6 sq. ft.

Xiaomi Smart Air Purifier Pro 4
Xiaomi Smart Air Purifier Pro 4

In addition, the Smart Pro 4 has a CADR of 500 CFM which, according to Xiaomi moves 8,330 L of clean air every minute.

Wind Speed Test

Our wind speed test uses an anemometer placed directly on the air vents of the Xiaomi Smart Air Purifier Pro 4 to measure the fan speeds in miles per hour. We run it on the lowest and highest fan speeds and record the speed of the air coming out of the device.

Minimum Wind Speed

0.2 mph

Maximum Wind Speed

12.1 mph

The maximum wind speed for the Xiaomi Pro 4 was 12.1 mpg, which is 0.5 mph above our testing average.

Xiaomi Pro 4 Windspeed Max
Xiaomi Pro 4 Windspeed Max

However, the Pro 4 had an impressively low minimum wind speed of 0.2 mph, being well below our testing average of 3.64 mph.


Build Quality Test

Our build quality test is a subjective test where we examine and assess the major material and design components of the air purifier. Specifically, we are looking for build and design issues that are more likely to break and/or be difficult to use.

Xiaomi Pro 4 Sideview
Xiaomi Pro 4 Sideview

The build quality of the Xiaomi Pro 4 received excellent scores in our assessment. Like most air purifiers, the Xiaomi is built out of plastic. While handling and moving the air purifier around the testing lab, it felt sturdy and well assembled.

PartBuild Quality
FanVery Good

Noise Test

To determine the level of noise that the Xiaomi Smart Air Purifier Pro 4 creates we use a sound meter and measure the decibel levels on both the lowest and highest fan speeds. In addition, we measure the ambient noise levels of the room as a baseline comparison.

Ambient Noise

44.5 dB

Min Noise

44.5 dB

Max Noise

57.8 dB

When placed on the highest setting, The Pro 4 had a measured decibel reading of 57.8 dB, which is 4.25 dB below our testing average of 62.08 dB. On its lowest setting, it had an impressive 44.5 dB reading, which was the same as our ambient measurements in the lab.



The Xiaomi Smart Air Purifier Pro 4 is called smart for a reason. It’s designed to improve usability using its internal sensors, a touch display, and app connectivity.



Setting up the device is as simple as unwrapping the product and plugging it in. Please note: the filter will come packaged inside the device. Make sure to remove the packaging surrounding the filter before plugging in the Pro 4 and turning it on.

Once the device is powered, it can start cleaning the surrounding air. However, if you want access to additional smart features, you will need to connect the device to the Mi Home app. Simply download the app and follow the in-app instructions to connect the Pro 4.


Controls & Display

When controlling the Xiaomi Smart Air Purifier Pro 4 you have three options: Touch panel, Mi Home app, and your voice.

Xiaomi Pro 4 Controls
Xiaomi Pro 4 Controls

With the touch display, you have two touch buttons that can turn on the device and cycle through the various modes. Here are the modes available with the Pro

With the touch display, you have two touch buttons that can turn on the device and cycle through the various modes. Here are the modes available with the Pro 4:

  • Auto mode
  • Sleep mode
  • Manual mode
  • Low speed
  • Medium speed
  • Max speed

Wireless Controls

To remotely control the device, you can use the Mi Home app. With the app, you get access to the same controls on the display, and other features like a timer or custom schedule. Additionally, you can check in real-time the current air quality information from the device. Through the Mi Home app you can connect your device to Amazon Alexa or Google Assistant, to control the device with your voice.

In The Box

Xiaomi Smart Air Purifier Pro 4 filter cover off
Xiaomi Smart Air Purifier Pro 4 filter cover off


The Xiaomi Smart Air Purifier Pro 4 has an estimated yearly maintenance cost of $50. The following are the major maintenance tasks for the Xiaomi Smart Air Purifier Pro 4.

TaskDescriptionEst. Annual Cost
HEPA FilterReplace every 12 months$50 (Main Filter)
Carbon FilterRemove tangles and any obstructions$50 (Main Filter)
Pre FilterWash as needed$0
SensorsWipe clean as needed$0

Size & Dimensions

In terms of size, I would consider the Xiaomi Pro 4 a medium-sized air purifier. It has a simple and tall design, with a modern aesthetic.

Height26.8″ (68.1 cm)
Length0.0″ (0.0 cm)
Width10.8″ (27.4 cm)
Weight15.0 lbs. (6.8 kg)


The following table details the product specifications according to the manufacturer.

Manufacturer Specifications
ModelSmart Air Purifier Pro 4
Height26.8″ (68.1 cm)
Length0.0″ (0.0 cm)
Width10.8″ (27.4 cm)
Weight15.0 lbs. (6.8 kg)
FilterCarbon, Pre-Filter, Ionizer
Noise Levels58 dB (max)
Coverage Area646 sq. ft.
Wi-Fi CompatibleYes
Warranty1 year
PriceCheck Price

Product Evolution

Xiaomi does have a line of smart home fan systems ranging from purifiers, fans, and humidifiers. The Pro 4 is the only full size air purification system offered by Xiaomi. The Xiaomi Smart 4 Compact however, is the smaller version of the Pro 4.

How does Xiaomi Smart Air Purifier Pro 4 compare?

Below is a complete list of our air purifier tests and critical product data compared side by side to the average based on all of our air purifier tests to date.

Test TypeTest DataAvg. Data
PM2.5 (2 hours)0.3 ppm0.2 ppm
PM10 (2 hours)0.4 ppm0.3 ppm
Particles (2 hours)5945
AQI (2 hours)11
Ozone Detected0.0 ppm0.0 ppm
Filter TypesCarbon, Pre-Filter, Ionizern/a
Coverage Area646 sq. ft.727 sq. ft.
Max Wind Speed12.1 mph12.1 mph
Noise Test57.8 dB61.8 dB

The Xiaomi Pro 4 showcased slightly worse than average purification performance reducing PM2.5 down to 0.3, while the average air purifier we’ve tested to date reduces PM2.5 down to 0.2.

In addition, the coverage area is less than 80.6 sq. ft. less than the testing average of 726.6 sq. ft. This is neither better or worse, but depends on your specific needs.

Finally, the Smart Pro 4 tends to run quieter than the average air purifier we test, creating 4.25 dB less noise than our testing average of 61.84.

Other Air Purifiers to Consider

Create simple block module

Airdoctor 5500

AirDoctor 5500

The AirDoctor 5500 is a large air purifier designed for large homes or small offices.

The AirDoctor 5500 would be an excellent choice for purification performance and large coverage. With its 6 patented filter designs, it can handle large open areas

Shark NeverChange

Shark Neverchange

The Shark NeverChange is from the latest HP300 air purifier series from Shark.

It offers a wide range of user settings and air quality display information. This would be an excellent choice for users that want a power on and forget system.

Oransi Mod+ Front

Oransi Mod+

The Oransi Mod+ is the successor to the Oransi Mod

This high performance air purification system is excellent for medium to large sized rooms that need superior purification.


Use Also Asked to find relevant FAQs. And/or just create a few of your own that you think are relevant in case where Also Asked isn’t providing good questions.

Does the Xiaomi Pro 4 have an Ionizer??

Yes, Xiaomi Pro 4 has an ionizer. The Ionizer is automatically turned on when the system is activated.

Can the Xiaomi Pro 4 remove the smell of smoke from cigarettes?

Depending on the environment and amount of smoke, it can help filter the air and remove the smoke. The Xiaomi Pro 4 uses a carbon filter (in addition to other filters), which can help to remove VOCs and odors. However, this is specific to air quality, not fabrics and other surfaces that can retain the cigarette smell.

Is the Xiaomi Pro 4 a True HEPA filter?

This specific model has a proprietary filter that is not HEPA.

About Derek Hales

Derek HalesDerek Hales is the Founder and Editor-in-Chief of He has been featured in Fast Company, Reader's Digest, Business Insider,, She Knows, and other major publications. Derek has a Bachelor's Degree in Business Administration from Kansas State University. Hales has been testing and reviewing products for the home since 2014.