Excellent in every aspect
Great product with a capability to reduce dust by approximately 3/4 e.g. if atmosphere pm2.5 is 300ppm , it will be reduced to upto 75ppm inside room , only if minimum ventilation is provided to take care the CO2 we generate.In my case , I have found in my area that the ambient has CO2 at ~410 ppm. If we open one window door to only by 5mm clearnce, the CO2 is being maintained from 500 to 600 ppm with 2 adults inside the room , based on wind velocity and direction. This adjustment 5mm clearance was achieved measuring with “calibrated stand alone CO2 cum PM 1.0, 2.5 , 10 measurement meter”One more example with above ventilation arrangement, the machine is in auto and ambient air pm2.5 at 198ppm, room also at 198 ppm, the fan speed reached medium (sound audible), it took some time to reach 85ppm and then it took 1min from 85 ppm to 68 ppm, now fan speed changed to low speed in Auto (sound is inaudible), this ppm starts increasing gradually to 85ppm in 1.5 minutes, now fan speed increases to medium again and the cycle repeats as long as outside pm 2.5 is 198ppm.Similarly the fan speed (so it’s sound) can be very high if ambient pollution is very high.It needs external cleaning of it’s HEPA filter every month based on pollution. The sensor may need cleaning every 3 months for accurate readings (if sensor mal functions , it is to be cleaned first and check before taking to any service center).It has a simple filter element with spare availability and capable to give atleast 3 times the specified life, if we clean the HEPA filter element externally with vacuum cleaner regularly.It does not have ozone producing UV rays or ion generators, which if not properly designed ( specified to customes not worry) may pollute the air with ozone.It has particulate count PM 2.5 meter which is very accurate, in addition it change display colour according to pollution zones to know the condition of air in the room (The readings were authenticated with above calibrated stand alone meter CO2, PM1.0, PM2.5 and PM10).We have to keep it on Auto to facilitate to change flow /speed based on pollution level (it’stemperature and humidity meters are also useful).Update 24.04.22 (still under warranty) : It developed some abnormal sound just audible , when we go near to it (like kitch, kitch, kitch..) at lowest speed. Doubt was on loosening of bottom locknut of fan and sound is ruled out from fan bearings, this diagnosis also strengthened by the observation that the above sound disappeared, when it is made upside down.Bottom cover opened , side covers opened , the bottom grill was moved down by lifting lock with columns and it was found that the button lock nut was in slightly loose condition as anticipated. The abnormal sound and mild vibration problems are resolved after tightening the nut (with 13mm tubular spanner already available with me), holding the fan (nut is a self locking type) and assembled back , But opening of side covers is a tricky and risky job (some locks may be broken, use hand gloves to protect hands from sharp edges , they may open in jerky motion ). I have made some top grill locks bottom side open by cutting (modification) so that I can open the panels easily in future. However another Mi Air purifier 2S is working almost continuously without any problem from last 3 years.Update: 02.07.22 High abnormal sound observed. This time I want send it to service center , but while lifting some material flied off from grill. So, when I run it upside down many foreign material came out like some bodies of flying ants , their wings and one baby lizard. Now again it is working normal.17.01.2023 The filter replaced as the flow became very low after 14 months of almost continuous use in high PM 2.5 conditions. Hence the time taken to reduce pm 2.5 had increased to an extend that it is unable reduce less than 150 , while ambient is at 300. The effectiveness restored after filter replacement.

Exceptional Performance After Replacement: Xiaomi Smart Air Purifier 4
I recently purchased the Xiaomi Smart Air Purifier 4, and although I initially encountered some performance issues with the first unit I received, the replacement product has been an absolute game-changer. The Xiaomi Smart Air Purifier 4 has proven to be an excellent investment, effectively improving the air quality in my home and providing a breath of fresh air.The design of the Xiaomi Smart Air Purifier 4 is sleek and modern, blending seamlessly into my home decor. The compact size allows for easy placement in any room, ensuring optimal air purification throughout the entire space. I particularly appreciate the intuitive touch controls and the informative LED display, which provides real-time updates on air quality and other important parameters.Once the replacement unit arrived, I was genuinely impressed by its performance. The Xiaomi Smart Air Purifier 4 boasts a powerful filtration system, effectively capturing and eliminating various airborne pollutants, including dust, pet dander, allergens, and even odors. With a high Clean Air Delivery Rate (CADR), it quickly circulates and cleans the air in large rooms, providing a refreshing environment for my family and me.The air purifier’s smart features are a true highlight. It can be connected to my smartphone via the Xiaomi Home app, enabling me to control and monitor air quality even when I’m away from home. The app offers valuable insights into air quality trends, allowing me to adjust the purifier settings remotely and ensuring the air is fresh and clean before I return.The replacement unit has been remarkably quiet in operation, allowing me to enjoy peaceful and undisturbed nights. Even when operating at higher fan speeds, the noise level remains tolerable and doesn’t disrupt daily activities or conversations. This aspect makes the Xiaomi Smart Air Purifier 4 suitable for bedrooms, living rooms, and even small workspaces.Although I faced initial performance issues with the first unit, the replacement product has truly exceeded my expectations. The Xiaomi Smart Air Purifier 4 is a reliable, efficient, and smart solution for improving indoor air quality. Its powerful filtration, sleek design, smart features, and low noise operation make it a standout product in its category.If you’re looking to enhance the air quality in your home or office, I highly recommend giving the Xiaomi Smart Air Purifier 4 a try. It has certainly made a positive impact on the air we breathe, and I am extremely satisfied with its performance after the replacement.