Unfortunately, the air quality in several parts of Europe has been worsening, resulting in tens of thousands of deaths every year. Furthermore, recent studies show that indoor air can be even more polluted than outdoors. No wonder, an air purifier can be a life-changer for people who live in polluted areas or suffer from asthma or allergies. Whether you wonder if you really need an air purifier, if it can protect you from COVID-19, what model is the most efficient or just want to know what CADR, HEPA, VOCs and all those other abbreviations mean, you have come to the right place.
Air Purifiers Buying Guide
The primary function of an air purifier is to remove fine particles and other pollutants from the air. However, these can vary from hair and dander to volatile gases, making this task rather tricky. Therefore, several filtration technologies are often used together.
Do I Really Need One?
As much as we love finding cool products, we don’t recommend ones that you don’t really need.
Thus, if you reside in an area where air pollution does not exceed the quality standards, and are, overall, a healthy person, an air purifier probably will not add much to your quality of life. Nevertheless, there are people to whom these devices can help a lot. If you live in a highly polluted area, have a compromised immune system, asthma, or allergies, getting one is a good idea. There is also research suggesting that these devices can help immunocompromised or asthmatic babies and children; thus, you might want to put one air purifier in the nursery.
Can It Protect Me from COVID-19?
The short answer is probably not. Even though the WHO has recognised that the airborne transmission is possible, and, theoretically, HEPA-filter air purifiers can capture viruses of the size of COVID-19, the primary transmission causes remain human-to-human contact and contact with contaminated surfaces. In other words, if you are joyfully chatting with someone who has been infected, an air purifier at the other end of the room will not manage to capture all the viruses before they reach you. Following the national recommendations will protect you more.
How does It Work?
Here’s what you should know about the various filtration methods used in air purifiers.
Pre-filter
Designed to catch larger particles, such as visible dust and pet hair, the pre-filter effectively helps to extend the lifetime of the primary filter. Thus, air purifiers with pre-filter are better suited for areas that have a lot of dust. Usually, pre-filters can be washed and/or vacuum cleaned. This means they last for a lifetime and replacements are not needed.
Mechanical filter
Think of the mechanical filter as a very fine screen that does not allow pollutant particles to pass through. In most air purifier models, this is the primary filtration mechanism.
The pollutant particles have different sizes, for example, the commonly mentioned PM2.5 refers to pollutants at the size of 2.5 microns (approximately 1/30th of the human hair). What’s wrong with their size? The PM2.5 particles are small enough to penetrate deep into the lungs or even enter the bloodstream. According to the EU standard, their concentration must be below 25 µg/m3.
Another commonly measured pollutant type is PM10, which means 10 microns or the approximate size of a human hair. These particles are visible to the eye; common examples are dust, pollen or mould. Their concentration in the air should remain below 40 µg/m3.
Basically, you want a mechanical filter that is as good at trapping bigger particles as the small ones. The golden standard in the air purifier world is HEPA. This commonly used abbreviation stands for high-efficiency particulate air, and these are hands-down best filters for people who have allergies or asthma. According to the European Standard, there are several classes. An H-13 filter (most commonly used in household appliances) should remove at least 99,95% of particles whose diameter is equal to 0.3 μm. An H-14 filter can remove even more, at least 99,995%. Lower-grade filters are called EPA (efficient particulate air), these, depending on their class, trap 85 to 99,5% of the ultrafine particles.
Several filtration mechanisms help to capture nearly all larger and finer pollutants, making HEPA filters excellent for fighting hair, dust, pollen, spores, mould and even some bacteria and viruses. However, they cannot help to get rid of gases or unpleasant smells. To maintain their efficiency, HEPA filters typically need to be changed every 12 to 18 months, and the replacements can be costly.
Proceed with caution when you see terms, such as “HEPA-like”, “HEPA-style” or just a new, revolutionary filtering technology that is said to be as or even more efficient than true-HEPA. Typically, that’s not the case. Finally, if you don’t have asthma or allergies, a simpler and cheaper filter than true-HEPA can still perform sufficiently for your needs and effectively trap the larger PM2.5 and PM10 particles.
Activated Carbon
To get rid of these, you will need a filter that contains adsorbent material. Activated carbon is the most common adsorbent used in air purifiers, but some filters use charcoal or specific minerals called zeolites. Nevertheless, the idea remains the same, these filters capture volatile organic compounds, often abbreviated as VOCs. VOCs are not only unpleasant odours from pets, cooking, or smoking; they can also be harmful gases released from cleaning products, new furniture or recently painted surfaces.
The problem with filters that are designed to capture VOCs is that usually, they contain a relatively small amount of adsorbent that gets saturated quickly. In such a case, not only will the filter fail to get rid of undesired aromas any longer, but it might also even start to release back some of the VOCs captured before. Some air purifier models offer special filters that contain more adsorbents and are marketed for odour prevention. Others allow changing the VOC filter independently from the main one, which helps to save a lot of money over time if dealing with smells is your primary reason for getting an air purifier.
Ionisation
Yes, we know, that the idea of ionisation sounds cool – emitting negative ions that cause pollutant particles to clump together. Then, they fall on a special plate or attach to surfaces around the house. Still, wherever they stick, that area will require frequent cleaning; thus, a special plate is a better option in our opinion. However, these filters don’t seem to add much if you already have HEPA in place. Furthermore, they emit ozone in the process that is a pollutant itself. Nowadays, the air purifiers with ionisation function get tested, and the amounts of ozone they give off are well below of what is considered harmful for human health (120 µg/m3 to be precise). Nevertheless, we would not recommend relying on this filtration as the primary method.
Electrostatic Filtration
As the name suggests, electrostatic filters use static electricity to impart particles that pass through the filter. This causes them to stick together similarly as a balloon sticks to a wool sweater. Electrostatic filtration method works well for capturing small particles, allergens and even some odours and gases; however, it cannot protect from bacteria and viruses.
UV-C Light
Some air purifiers use the UV-C light to eliminates viruses, bacteria, pathogens, and mould. However, this technology is not effective against particulates, gases, or odours. The UV bulbs need regular cleaning and replacement, according to the manufacturer’s instructions. UV-C light is harmless to humans; however, just like ionisation this technology alone has limited efficiency.
What else to Look for?
While the filter undoubtedly is the most essential part of the air purifier, some other features (or lack of them) may affect your choice and how satisfied you will be with your purchase.
Shape & Size
There’s no denying, your newly acquired air purifier will prominently occupy some of your floor- or tablespace. Bigger models usually tend to be more potent; however, this is not universal. Remember that you will not be able to tuck the air purifier in the corner. To ensure optimal air exchange, leave at least 10 cm of space around it from all sides, some models will need more.
Oscillation
Distributing air in just one direction may not ensure optimal air exchange, especially in larger rooms. Thus, higher-end models typically change the air distribution direction automatically, creating more complex flow patterns. Oscillation also matters if your air purifier doubles-up as a fan, since a strong, one-directional stream of air can be unpleasant in some situations.
Sensors
Many air purifiers come with sensors that allow the user to stay informed about any changes in air quality. Models that have sensors usually also come with an automatic mode. This means that the device adjusts fan speed according to the pollution levels. However, some data is suggesting that the automatic modes may not be sufficient to effectively remove the pollutants. If you have severe asthma or allergies, we recommend leaving the air purifier on medium speed rather than auto. Even if its sensors are sharp, the pre-set pollution threshold after which the device automatically picks up speed might be too high to efficiently alleviate your symptoms. The same advice goes regarding the night mode.
Display
Models with sensors usually feature a small screen that, depending on the model, can inform about the air quality, the chosen operation mode, the remaining filter lifetime and so on. Air purifiers without display are much cheaper and usually come with indicator lights that inform the user on how they are doing.
Timer
This is another feature that allows saving energy and extending the filter life. Some of the more advanced air purifier models will enable the user to set operation times. If you live in an area where air quality is within norms and often leave the house for extended periods, this feature can get handy.
Smart Controls
Air purifier models that can be controlled via a smartphone app or voice assistant are becoming more and more popular. Smart controls can give you more nuanced options to adjust the device settings according to your wishes. However, buttons and remote controls work equally well and are cheaper.
Will it be powerful enough?
Most manufacturers offer pre-calculated square meter ratings of their air purifier models. This might seem helpful; however, a few aspects must be considered. First, there is no uniform standard. These ratings are estimated using different methods, which means they can be inflated to impress the customers. Secondly, figures in laboratory tests do not necessarily reflect real-life circumstances. Thirdly, the ceiling height is not taken into account in square meter ratings; higher-than-average ceiling (above 2,4 m) will mean lower effective area. Finally, the purifiers are often tested when set on their maximum fan speed (and when their filters are brand new). Considering all this, we recommend picking a model that has been rated for larger areas than your actual room size.
One of the most common methods used to rate air purifiers is the so-called CADR test. CADR stands for Clean Air Delivery Rate, and this standard was developed by the Association of Home Appliance Manufacturers (AHAM). The rating is expressed in cubic meters per hour (or cubic feet per minute), indicating how much air the purifier cleans in a given time. Usually, three different pollutants are measured – tobacco smoke, dust and pollen. Higher CADR rating means faster and more effective filtering, and certified models get re-tested from time to time to make sure the rating remains accurate.
If you or people you live with suffer from respiratory ailments, aim for ACH of 4 or higher. Even if you are healthy, we don’t recommend picking a model of ACH below 2. Here is a simple and useful calculator that provides ideal CADR for your room size, taking into account the ACH.
How to Use It?
Now that you know what your perfect purifier shall look and perform like, here are some tips to get the most of its functions:
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Ideally, you want one air purifier per room. If that’s too expensive, prioritise areas where you spend the most time, such as bedroom, nursery, home office etc.
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Place the air purifier 10 to 30 cm away from obstacles to ensure optimal air circulation and redistribution.
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Before switching the air purifier on for the first time, make sure you have removed all the protective packaging from the device itself and its filters.
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Leave the appliance on high speed for one hour or so, afterwards reduce the fan speed to medium and keep it that way. If your purifier has more than three speeds, pick the highest one that you still find quiet enough to carry out everyday activities (it should be below 50 dB).
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When the purifier is running, keep the windows and doors closed. A constant flow of unfiltered air can be higher than your purifier can effectively handle.
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Replace and/or clean the filters as suggested in the manual. Remember that dirty filters may not trap the pollutants sufficiently.
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Clean the housing and pre-filter with a vacuum cleaner from dust at least once per month. When you change the primary filter, it is a good idea to vacuum the inner part as well.