Xiaomi Smart Air Purifier 4, Best Purified Air Delivery Rate 387 m3/hr, True HEPA, traps 99.99% Virus, High coverage: 516 Sq Ft, Fast Purification in 7 Mins, RoHS & Allergy Care Certified, Alexa&GA

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.

Its excellent purifier. AQI reduced from 250 to 20 in flat 45 minutes in a big drawing room. Luttle overpriced.

The purifier works great on all aspects, right from cleansing of air to smart design occupying minimal space, light in weight and very less noise. The indicator is very good and accurate and one can actually feel the difference in the quality of the air, purified and not purified. Very easily controlled through a customer friendly app. Absolutely recommended for master bedroom size rooms.

Good Efficiency, light weight, less noise, परफेक्ट for every home, compact sizes

One of the best air purifiers out there. in just about 10 mins it drastically approves the air quality of the room, it is practically soundless. easy to set up. it is not portable though. the plug is a setient plug (2 pin plug). compatible with indian switch boards. the display also indiciates temperature and humidity level.

It's a good product no doubts But after few months the sensor won't work properly Even I cleaned it as mentioned still I don't think it's detecting the air particles properly

I Would say this is a Worth for money product at its price range. I am someone who believes in Effectiveness more than gimmicks, so i am writing an honest review 5 months after purchase. 1. Does it Purity the Air and how fast ? Ans. Yes its is effective at purifying the air, so it does its core Job effectively. the room i am using this one is around 16x16 room, and it purifies the air in it in 15-20 minutes approx, brings the AQI from 300+ to around 50-15. 2. Regarding the Other extra features, The negative air ionization and odours elimination, i do not think it is that effective though, even though its not a concern for me honestly. 3. Lastly i like the App and its information a lot, in helps us keep track of certain information apart from just pollution level like the humidity, temperature and most importantly the Filter life. i have given this a 5 star as it served my purpose of providing me clean air in a specific room size and that too quickly, couldn't really care of the gimmicky features except the app connection is actually very helpful in real life.

After 2 years of use, the air purifier is as good as dead. Problem is that it keeps turning ON/OFF. There is no automation/scene set. First i though that it could be a filter issue so I replaced the filter with original one bought from Mi.com but no resolution. I tried contacting the official service center but they denied even looking at the filter, stating that no product support as it is out of warranty. Also to note that they mentioned that Mi air purifiers cannot be repaired and during warranty if there is a problem, they replace the entire unit. Tried posting on reddit, Xiaomi official Facebook chat, but no support. Be cautious of spending approx 15k on this air purifier because of no service availability. I am now regretting spending so much. It once looked fascinating with so many features but after 2 years it is just an e-waste of zero value.