Air purifiers seem to be here to stay. The arrival of Chinese brands in the European household appliances market has meant that we can currently find in stores a range of devices of this type much more extensive than we could have imagined a few years ago. How far apart some designs are from each other and their enormous variety of prices are surprising, but, above all, technology amazes that it is necessary to prepare for these devices to fulfil what they promise.
And is that removing most of the particles and impurities suspended in the air we breathe is a real challenge. On the one hand, it is necessary to develop a filter that is capable of retaining particles with a size significantly less than 1 micron (The thickness of a human hair ranges from 15 to 170 microns). And, in addition, it is also important to have a sensor that is capable of accurately monitoring the degree of air pollution to act dynamically on the operating regime of the purifier. This Xiaomi product has, on paper, these two assets. And it also has an attractive price, so we couldn’t resist testing it to see if it really lives up to what it promises.
Xiaomi Mi Air Purifier 3H: technical specifications
Air purifiers don’t usually require that we pay much attention to them. It is desirable that they interfere in our daily routine as little as possible, and to achieve this they usually incorporate an automatic operating mode that adapts their filtering capacity to the level of air pollution at a given moment. This Xiaomi model incorporates this function, but, like other purifiers of this brand, it has a screen OLED, touch and circular to which we can resort to act on its operation or find out in which mode it is working (as we will see later it is also possible to manage the behaviour of the purifier using an app that we can install on our smartphone).
The CADR (‘Clean Air Delivery Rate’) parameter indicates the airflow that the purifier is capable of treating in one hour. This Xiaomi device processes 380 m³ of air in this period of time
According to Xiaomi, the filter that is responsible for removing polluting elements from the air is capable of capturing particles with a minimum size of 0.3 microns, which, as we have seen two paragraphs above, indicates that they can be much smaller than the thickness of a human hair. If we stick to this figure it is evident that its filtering capacity, on paper, is very respectable. In fact, the particle retention capacity of this HEPA filter (this Anglo-Saxon acronym stands for ‘high-efficiency air particulate filter’) is similar to that of filters used to treat the air in aircraft cabins, industrial clean rooms and critical hospital rooms.
In the table that you have below these lines, you can see that there are two fields called CADR with which most of the users are probably not familiar, so it is worth reviewing what they consist of. The acronym CADR comes from the English term Clean Air Delivery Rate and indicates the airflow that the purifier is capable of treating in one hour. As you can see in the table, this Xiaomi device manages to retain 99.97% of the particles suspended in the air that measure 0.3 microns or more. Furthermore, it is capable of processing 380 m³ of air in one hour, and also manages to remove formaldehyde from 60 m³ of air in the same period of time (formaldehyde is a colourless substance that is usually present in wooden furniture, insulating materials and other elements that we all have at home).
|XIAOMI MI AIR PURIFIER 3H||characteristics|
|SCREEN||Circular touch OLED with a diameter of 52 mm|
|FILTER TYPE||360 ° three-layer cylindrical HEPA|
|MAXIMUM SIZE OF THE ROOM TO PURIFY||45 square meters|
|CADR (PARTICLES)||380 m³ / h|
|CADR (FORMALDEHYDE)||60 m³ / h|
|DISPOSAL OF PARTICLES OF 0.3 μm||99.97%|
|MAXIMUM NOISE LEVEL||64 dB|
|FILTER LIFE||From 6 to 12 months|
|WIRELESS CONNECTIVITY||WiFi 802.11b / g / n|
|SUPPORTED VOICE ASSISTANTS||Google Assistant and Amazon Alexa|
|DIMENSIONS||240 × 240 × 520 mm|
The particle filter: the true heart of this air purifier
The filter that Xiaomi has developed for this purifier is a hollow cylinder-shaped device that is made up of three layers of different material so that each one has the responsibility of capturing particles in a range of different sizes. The outermost layer is shaped like a grid and is responsible for retaining the largest airborne elements, such as hair, dust, pollen or cotton and paper fibres, among other particles. The second layer, the middle one, is a HEPA filter that is responsible for capturing, according to Xiaomi, up to 99.97% of the particles They have a size of up to 0.3 microns, as well as retain particles with a minimum size of 0.1 microns. Its filtering capacity of these last particles is not as high as that of retention of those that measure 0.3 microns or more.
This intermediate layer of the filter is responsible for dealing with many of the allergens that affect many people, especially during the spring months. And also with the particles that tobacco smoke contains. But this is not all. The size of the bacteria ranges from 10 to 0.2 microns (scientists hypothesize that there are also nanobacteria that are even smaller), and the diameter of the viruses ranges from 0.5 to 0.02 microns, which indicates that this HEPA filter should be capable of capture most of the bacteria and a respectable range of viruses (those with a diameter of less than 0.1 micron will get through).
We still have to examine what the third layer of the filter does, the innermost. You can see what it looks like in the following detail photograph. This layer is an activated carbon filter designed to absorb formaldehyde (it is the substance that we have talked about a few paragraphs above), the volatile organic compounds that are usually responsible for bad odour and some other harmful substances, such as, for example, toluene, a toxic hydrocarbon that is It is used as a solvent in paint and it is also present in many of the coatings that we have at home.
The air that the filter must purify accesses the interior of the purifier through holes made in the sidewalls of the device. From an aesthetic point of view this design looks great, but what really makes these small holes important is that they favour air circulation from the outside to the inside of the purifier as a result of the pressure difference generated by the housed centrifugal fan inside the device. According to Xiaomi, this fan manages to displace a flow of 6,330 litres of air per minute when working at maximum power, a figure that in theory seems sufficient to keep the air of a room with a considerable size purified (the Chinese brand assures that this purifier can process the air of rooms of up to 45 square meters).
The pressure difference generated by the centrifugal fan inside the device compared to the one outside causes a large amount of air to enter through the holes in the walls. When accessing the interior of the apparatus, the air is forced to pass through the particle filter, and just afterwards it moves upwards through a pressurized air duct It has polished walls to offer the least resistance to airflow displacement. When it reaches the top of the purifier, clean air comes out of the device through a grill that occupies almost its entire surface (measures 240 x 240 mm).
Using it is a piece of cake both from the app and from the OLED screen
As I have advanced in the first paragraphs of this analysis, we can act on the operation of this air purifier in two different ways: using Xiaomi’s Mi Home app, which is available for both Android and iOS, or by resorting to the circular OLED screen housed at the top of the device’s front panel. The app incorporates a wizard that will guide us through the procedure we must follow to connect the purifier to our wireless network, but in essence, the only thing we must do is activate the Bluetooth connection of the mobile and place ourselves near the purifier so that the smartphone can transfer it the parameters of connection to the WiFi network.
We can control the operation of this purifier from its OLED screen or from the Mi Home app that we can install on our smartphone
An important tip that can save you headaches if you buy this product from Xiaomi: for the connection between our mobile phone and the air purifier to be carried out successfully, it is essential that we make sure that the Mi Home app you have permission to use geolocation from our mobile (usually we can check it from Settings / Applications / Xiaomi Home). Otherwise, the connection will not be successful and we will not be able to connect the purifier to our WiFi network. This does not mean that we cannot use it. We can do it, but we will only control it from the integrated OLED screen, and not from the app that allows us to manipulate it from our mobile phone.
As you can see in the captures that we publish below these lines, the main screen of the app reflects the air quality of the room in which we have installed the purifier, the ambient temperature and the percentage of air humidity. From here we can also turn the device on and off remotely, as well as activate any of the four predefined operating modes that it implements: automatic (the purifier itself adapts its filtering regime to the characteristics of the air at a given moment), rest (reduces the rotation speed of the fan to emit a minimum noise level and not disturb us at night), variable speed (allows us to force the speed at which the air must be processed choosing between three different intensities) and favorite (to predefine the working conditions of the device to our liking).
The OLED screen housed in the front panel of the purifier offers us at a glance essentially the same information that we can find in the Xiaomi app: air quality, ambient temperature, humidity percentage and operating mode. If the air quality is high, the ring that we can see at the bottom of the screen will turn green; if it is average it will turn orange; and finally, if the air quality is low, the ring will be red. The number at the top of the screen counts the amount of PM2.5 particles, which is a classification system for particles that cares for their diameter.
The PM value is a parameter that is used to classify small particles by evaluating their diameter. This purifier quantifies PM2.5 particles, which have a diameter of 2.5 microns or less.
PM2.5 particles have a diameter of 2.5 microns or less, so we can inhale them easily. If the purifier perceives that the air contains less than 75 μg / m³ of these particles, the ring will turn green to indicate that the air we are breathing is of good quality. If the amount of PM2.5 particles ranges from 75 to 150 μg / m³ the ring will turn orange. And if the quantity of particles is greater than 150 μg / m³, the ring will acquire the red color to indicate that the air we are breathing contains a high level of suspended particles, and, therefore, it has poor quality.
There is a button on the rear panel of the air purifier that we can use to turn off the OLED screen when we want it to stop emitting light. This feature is interesting if we place it in a bedroom and we do not want the light emitted by the screen to disturb us at night. An interesting note: the small hole that you can see in the following detail photograph, just to the left of the on-off button on the screen, reveals the location of the sensor that is responsible for measure temperature and humidity of the room.
Performance in combat: this is how we managed to put you in trouble
If there is a component that can discuss the particulate filter its role in this air purifier, that is, without a doubt, the laser sensor that is hidden on the other side of the grid that you can see in the following detail photograph. This sensor is responsible for identifying and accounting for PM2.5 particles suspended in the air in order to adapt the device’s operating regime in real-time to the quality of the air at a given moment. When we activate the automatic operating mode, this sensor begins to monitor the air quality, so that the information it collects is used by the purifier software to proactively regulate the speed of the fan. And, therefore, also the airflow that is being processed by the device.
Testing an air purifier is not easy, especially if you live away from a big city and only 50 meters away from a huge pine forest that acts like a gigantic “green” lung. When I connected this air purifier to my wireless network and set it up it started to measure a PM2.5 value of only ‘001’, which means that the air that I usually breathe in my house has only 1 μg / m³ of these particles in suspension. Even so, I was not willing to give up the possibility of subjecting it to as much stress as possible, so it occurred to me to collect dust and pollen in sufficient quantity to significantly affect the air quality of the room where I had installed the purifier. And yes, I got away with it.
I tossed it into the air in the opposite corner of the room to check how long it took for the purifier’s laser sensor to identify what had happened, and in just 20 seconds the centrifugal fan started increasing its spin rate automatically to increase the airflow it was processing the filter. The OLED display went from reflecting the usual PM2.5 value ‘001’ and its green ring to entering a value of ‘086’ and tinting the ring in bright orange. The air had gone from containing just 1 μg / m³ of suspended particles to being saturated with 86 μg / m³. Little by little, the filter was purifying the air and approximately thirty minutes later the OLED screen reflected the usual ‘001’ value again. The purifier had passed this test successfully.
I was still missing something else: examining the filter to see first hand where the dust and pollen particles that had poured into the air a few minutes before had gone. Due to their diameter, it is logical that most of them were captured by the second layer of the filter, which is not exposed to sight, but he was sure that some larger rest had to have been stopped by the grid that makes up the first layer of the filter. So it was. In the following photograph, you can see some fibres of a certain size that they were lodged in the surface of the filter and therefore did not penetrate inside it.
The particle filter lasts, according to Xiaomi, between 6 and 12 months, and each replacement has an approximate price of 35 euros
This invites us to ask ourselves an important question: how long does the filter of this air purifier last? According to Xiaomi, its useful life fluctuates between 6 and 12 months, and each replacement costs just over 35 euros. We will know that the time has come to change it when the purifier software indicates it to us, either by notifying us through the OLED screen (each time we turn it on it indicates the percentage of degradation of the particle filter), or through the app that we have installed on our mobile phone.
Another important feature of air purifiers that users are interested in paying attention to is their noise emission level. The most reasonable thing is that we have this device on most of the day in automatic mode, so if it emits more noise than it should be annoying. It can even subject us to a certain degree of stress without us realizing it. Fortunately, this Xiaomi device is reasonably quiet. If we force the fan to operate with the maximum speed of rotation the noise, logically, increases, but if we keep it automatic for most of the time the noise it emits ranges from 37 to 39 dB. We will not perceive it unless we get close and pay attention. To measure noise I used my usual Velleman DVM805 reference sound level meter.
We come to the last test: the measurement of your consumption. In the specifications of this Xiaomi purifier, it announces a maximum consumption of 38 watts, and I have measured with my consumption meter about 27.2 watts under normal operating conditions, which occur when the fan is not forced to work at its maximum speed. It is not a negligible consumption, but, without a doubt, it is an acceptable figure as long as we find that a device like this has a beneficial impact on the air quality of our home.
Xiaomi Mi Air Purifier 3H: Xataka’s opinion
This air purifier does its job. Unfortunately, I don’t have the necessary equipment to find out if it is as effective in the process of eliminating bacteria and viruses as Xiaomi promises (this feature can only be accurately evaluated using laboratory equipment that is not easy to access), but if we stick to its ability to retain fibres, dust, pollen and bad odours, it works. I have tried it for three weeks and not only has it left a good taste in my mouth for its performance (a curiosity: once installed it is very noticeable that less dust accumulates on furniture); I am also convinced by its design and its moderate level of noise emission.
This purifier can have a positive impact on the health of people allergic to pollen, mites or other elements that can be suspended in the air
The only downside of a certain entity that I can put is that it seems to be a bulky device. Its plant is not excessive (it measures 24 x 24 cm), but it is 52 cm high and should not be placed next to a corner, so it is possible that in some rooms we may be forced to place it in a location where it can get in the way. It is also important that we consider the price of filter parts. The little more than 35 euros that each of them costs does not seem excessive if we change the filter once a year, but if we are forced to renew it every six months, some users may discard it. Of course, this is all the maintenance it requires. All we have to do is take the opportunity to clean the filter compartment when we change it.
In my opinion, people living in the countryside or other areas with a low level of air pollution can do without a device like this, unless they are allergic to pollen, mites or other elements that can be suspended in the air. In this case, they could benefit from a purifier like this. But I would recommend it without hesitation for anyone who lives in the centre of a big city, especially if they also have allergies similar to the ones I just mentioned. This air purifier, or another with comparable performance, could have a beneficial impact on your health. Honestly, I think that in these circumstances it is worth giving these types of devices a try.