Air cleaner: What filter technologies are out there and how do they perform? 

Multiple studies have shown that even short-term exposure to air pollution can have health consequences. Long-term exposure to air pollutants increases the risk of severe symptoms and has long-term consequences for the human body.
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Depending on the degree and duration of exposure, as well as the type of pollutant inhaled, the effects can vary. In addition to simple symptoms such as coughing and respiratory irritation, air pollution can cause acute conditions such as asthma, chronic lung disease, and more serious symptoms such as cardiovascular disease, impaired lung function, and respiratory infections. The World Health Organization (WHO) also indicates links between exposure to air pollution and diabetes, systemic inflammation, and neurodevelopmental disorders in children (Reference).

What are the advantages of an air purifier?

  • Pollutants are filtered from the air
  • Provides improved air quality
  • Relieves asthma symptoms
  • Neutralizes unpleasant odors
  • Improves sleep & concentration
  • Reduces risk of lung and heart disease

How does an air cleaner work?

The way an air purifier works is relatively simple. In most systems, the air in the room is drawn in by a fan and then passed through a filter, which collects the particles and pollutants contained in the air. The purified air then flows back out of the device.

What filter technologies are existing?

There are several different filter technologies on the market that are used for air purifiers these days. Here is an overview of the most important technologies:

a) HEPA Filter

HEPA filter (High-Efficiency Particulate Air) is a widely used technology for air purifiers. This type of filter was developed back in the 1940s as part of the Manhattan Project to remove dangerous radioactive particles from indoor air. HEPA filters consist of a fabric that resembles a mesh. Particles are trapped by the mesh as the air passes through it. HEPA filters can effectively filter larger particles such as pet dander, pollen, and dust mites. However, VOCs, viruses, bacteria, and small particles under 0.3 microns cannot be safely removed from the air with a HEPA-based air purifier. This type of filter must be changed at regular intervals because over time it becomes clogged and is no longer able to filter particles effectively.

b) PECO Filter

In PECO (Photo Electrochemical Oxidation) filters, ultraviolet A light is shone onto a filter membrane coated with nanoparticles. This creates a photoelectrochemical reaction on the surface of the filter that breaks down the molecular structure of organic particles in the air. Over time, larger particles that escape the pre-filter can partially block the light from reaching the surface of the PECO filter, reducing its efficiency. PECO filters, like HEPA filters, therefore require regular replacement; usually every 6 months.

c) Ionizer

In a filter with ionization, ions are positively charged so that dust particles in the air attach to them, and this electrostatic interaction causes several particles to form a cluster. These clusters can then be filtered more easily by the air purifier. In the process, however, harmful ozone is produced. Even though ionizers do not have a filter in the usual sense, regular cleaning is still necessary because the so-called collector attracts the pollutants from the air and continues to accumulate them. After some time of use, a layer of dirt forms on the collector, which should be washed off. For this purpose, the collector can be held under running water. Then the collector has to be left to dry.

d) Plasma Filter

Air purifiers with plasma filters use a comparatively new technology and have the ability to capture even the smallest particles that other types of filters cannot capture. A plasma filter generates ions that electrically charge air pollutants within the air purifier so that they can be separated in the subsequent collector. In this way, pollutants even as small as 0.01 micrometers can be removed from the air. Despite high efficiency, no harmful ozone is produced. Unlike other air purifiers, there is no need to change the filter either. Instead, the collector can simply be removed from the device and rinsed with water or cleaned in the dishwasher.

e) UVC Filter

With this technology, potential viruses from the air are irradiated with short-wave ultraviolet (UVC) light thus being killed, and then the “purified” air is released back into the room. The effectiveness against infectious aerosols in an indoor environment depends on a couple of things – whether a device can disinfect a sufficiently large volume of air, and whether the purified air can circulate well in the room. The efficacy also depends on the irradiation intensity and on the irradiation time of the air in the device. However, UV-C radiation poses a high health risk unless it is shielded by the device.

f) Activated Carbon Filter

An activated carbon Filter works similar to a sponge, pulling unwanted odors, gases and substances out of the air. The main component of an activated carbon filter, as the name suggests, is carbon. When the porous structure of the carbon is combined with hydrogen, oxygen or carbon dioxide, more fine pores are formed thus purifying the air from unpleasant odors and gases. However, these pores have a limited absorption capacity. Therefore, even with an air purifier with activated carbon filter, regular replacement of the filter has to be undertaken as a part of the care of the device. Many models have an interlock function to ensure high air quality at all times. As soon as the filter is filled, the air purifier shuts down so that no pollutants can be released into the surrounding air. Depending on the degree of air pollution, this is usually the case every four to six months.

Plants as air purifiers - a myth?

Houseplants are decorative and can create a homely atmosphere. However, the recurring claim that plants also help clean our indoor air is nothing but an urban myth. In fact, plants suffer from air pollution almost as much as we do. Instead of eliminating it, they become covered by it, thus limiting their ability to produce and release clean air. Research has shown that about a hundred plants per square meter would be needed to reduce volatile organic compounds (VOCs) to an extent that actually impacts air quality. Nevertheless, houseplants do have a positive effect on our well-being. They create a feeling of freshness and comfort.

Which air purifier is right for me?

At the end of the day, which air purifier technology to choose depends heavily on personal needs and preferences. To simplify the decision, the following questions should be answered in advance:

  • What is the air purifier needed for?
  • Do you have any health problems (asthma, allergy, lung or heart disease)?
  • Are the rooms particularly exposed to many pollutants (pets, smoke, pollen, odors)?
  • What type of filter do you prefer?
  • What is the size of the room where the air purifier will be used?
In our article “The best air purifier 2021” we present criteria to consider before buying an air purifier. After all, not every air purifier is equally suitable for all needs.

The ideal place for an air purifier

Often the kitchen and living room have poorer air quality than most other areas. This is mainly due to cooking, especially frying or burning food. In addition, kitchens are often cleaned with chemical substances that can  contribute to poor air quality. 

In the living room, candles and smoking are common but avoidable scenarios that worsen indoor air. Our home offices are also affected by poor air quality, which actually has a negative impact on concentration and productivity. According to some studies, performance drops by up to 50-60% depending on the level of air pollution in the rooms where we work.