Since Corona, everyone knows – germs spread very readily, very well and very often in the form of aerosols through the air and you can get sick. Likewise, small particles or odors can very much limit your well-being, even if you don't get sick by breathing them in. What helps best against all these particles in the air? In fact, airing is still the best method to get rid of annoying odors and aerosols, but this does not always work or is not always advisable in the case of allergens. Therefore, very common are air purification and air disinfection devices based on different technologies - filters, ionization, plasma, ozone or UVC radiation are used to make the direct ambient air free from particles and germs. But what are the differences? What are the advantages or disadvantages of the various room air cleaners? The hygiene experts from UVIS took a closer look on all the air cleaning technologies.
Fresh air – so nice when you can breathe it in deeply, it fills your lungs and, sneezing and coughing follows, you wrinkle your nose because it smells funny or you promptly caught some germ. Therefore, some people think about buying a room air purifier, which eliminates the smallest particles, odors, and pathogens in the air. In our article, we wanted to discuss the different technologies, the advantages and disadvantages, and the possible use cases of room air purifiers.
What are the arguments in favor of an air purifier?
What are the reasons to buy a room air purifier? Some. Take allergies, for example. Over 34 percent of women and around 27 percent of men in Germany suffer from an allergy, and of these, over 62 percent react to pollen from trees, bushes or grasses. Almost one in four Germans states that they are allergic to house dust or mites, and animal hair allergy ranks third with over 21 percent of allergy sufferers. However, it is not only allergens in the air that can affect our health, but also pathogens such as viruses, bacteria or fungi, and we have known for a long time that these germs are also readily transmitted through the air in the form of aerosols.
However, it is not only the particles that can make people ill, but also unpleasant odors that can have a considerable impact on the indoor climate. The smell of dog, cat or small animal, which does not bother the animal lover can become very unpleasant for visitors. It is the same with smokers or better non-smokers. The smell can be unbearable. It is not even necessary to smoke in the room, just the vapors from the clothes can be very disturbing.
But air purification devices are not only used against allergens and odors, but also against fine dust. Fine particles, which are released into the air by exhaust fumes from road traffic, power stations and district heating plants, as well as stoves and heaters in residential buildings, have been proven to cause serious lung diseases in humans, such as asthma, bronchitis or COPD (chronic obstructive pulmonary disease), or even cancer. That is the reason why all major German cities now have environmental zones to reduce fine dust pollution. The different air filter systems can contribute in interior areas substantially to the increase of the air and thereby quality of life.
Different indoor air purification technologies
Triple, quintuple, HEPA, with or without plasma or ions or UVC? Many persons are simply overwhelmed when deciding on the most suitable or best air purifier. Basically, the various room air purifier technologies are divided into:
Several technologies can also be used in one air cleaner. Which criteria can be relevant for the buying decision, we describe in the last paragraph.
Room air purifier with filter technology
There are air cleaners with different filters. These are divided into 17 different classes according to DIN (German quality specifications), from G1 to G4 for coarse filters, which filter out coarse dust in air-conditioning or exhaust air systems, for example, to F5 to F9, which can filter fine particles such as pollen or fine dust, to the HEPA filters from H10 to H14 and U15 to U17 for ultra-fine filter performance. Depending on the quality, these are also known as HEPA or ULPA filters – HEPA stands for "High- Efficency Particulate Air" and ULPA for "Ultra Low Penetration Air". In addition, there are also activated carbon filters that bind odors and gaseous compounds such as formaldehyde. These filters are also used in cooker hoods, for example, to minimize kitchen odors.
The air is sucked into the air purifier and passed through the various filters from coarse to very fine. In the process, dust, pollen and also germs get caught in the fabric filters and the air is discharged purified. An additional activated carbon filter binds odors and gaseous compounds.
To filter not only dust and pollen, but also pathogens from the air, modern, mobile filter units should be equipped with highly efficient fabric filters (filter classes H13 or H14) if possible, as only these effectively remove viruses from the air. But the filter devices have a small catch: the filters - full of dust, pollen, and germs - have to be changed after a certain period of time. Usually this is between six months and a year, and it should be done by professionals. Depending on the germ load and the place of installation, a filter change must even be carried out with protective clothing, and if the change is not done regularly, the air purification device can also become a germ trap. As with an activated carbon filter in the kitchen, which at some point no longer filters odors, germs can also be released again.
Air purifiers with UV-C technology
UVC radiation is the high-energy part of sunlight, which is actually completely filtered by the ozone layer. Therefore, we use only artificial UVC light for disinfection. The fact that UVC radiation inactivates germs of all kinds has been known for over 100 years and this technology has also been used for a very long time in medicine and in the food industry or for water treatment. UVC radiation penetrates the cell and destroys the DNA, the genetic material of the cell. Consequently, the cell can no longer reproduce and becomes inactive.
Air contaminated with germs is introduced into the unit and disinfected by the UVC radiation by inactivating the germs' genetic material. This renders them harmless. The disinfected air is then released back into the room.
If this effective technology is used for air purification, then one should make sure, however, that the so-called air circulation rate of the device corresponds to the room size and the lamps have enough power to disinfect the air in the desired time window. But caution is also required with the devices because the radiation is harmful not only for the germs, but also for us humans. A UVC lamp should never shine openly, but only in the closed device. However, modern mobile air disinfection units with UVC technology also have advantages over filter units - the noise level is much lower and there is no need to change filters. However, the devices are also available in combination - air purification with filters and additionally air disinfection with UVC radiation.
Air purifier plasma technology
Plasma is the fourth state of matter after solid, liquid and gas. Plasmas also occur in nature. For example, lightning is hot plasma and the northern lights are cold plasma. For air disinfection, so-called atmospheric pressure plasmas are used as cold plasmas. When a high electrical voltage is applied to a gas under atmospheric pressure, in our case atmospheric oxygen, the gas atoms split into ions, electrons and radicals. These then react with surfaces such as the cell membrane, deactivating the germs and thus rendering them harmless.
Air contaminated with germs is passed by plasma coils. The germs are inactivated and the disinfected air is released back into the room.
As with UVC technology, this method destroys the DNA of germs, rendering them harmless. The advantage of plasma technology is that it also eliminates odors, fine dust and volatile organic compounds and requires very little maintenance.
Here, too, however, it is important to match the capacity of the device with the size of the room and to use only those devices that cannot produce ozone as a waste product, because that would again be harmful to us humans.
Ozone technology for air disinfection
Yes, even though it can be harmful to us in direct contact or better when inhaled, ozone can be used to disinfect very well. It is used in the food industry to preserve food, in hospitals to disinfect operating rooms or even to disinfect water. From a so-called ozone generator, popularly known as ozonator, the triatomic ozone is produced from oxygen by electrical corona discharges.
1 - Air is drawn in by the fan through the filter.
2 - Fan circulates air further.
3 - Oxygen molecules are split by electrical discharge.
4 - Ozone is formed. It binds and destroys odors and harmful substances.
The gas is blown into the room by the device, spreads there very quickly even to areas that are difficult to access, penetrates the tissue and destroys the cells it attacks by oxidation. However, this affects not only viruses, bacteria or fungi, but also our cells. Therefore, when ozone is used for disinfection, no one should be in the room, even for a long period of time. However, since ozone is very unstable, it decomposes over time and turns back into oxygen. After about 30 minutes, a room disinfected with ozone can be entered again. Thus, with appropriate precautions and under certain conditions, ozone can be used by professionals for disinfection.
Effectiveness of air purifiers
In order to find the best air purifier and then for it to be effective, there are a few factors to consider: How big is the room, or more precisely, how much air can the particular air purifier circulate per hour? How many people usually stay in the room?
An air cleaner in your own home usually does not need to be as powerful as an air cleaner for the office, where several people are constantly present. Where the room air purifier is placed is also crucial. For example, in the case of air purifiers with filters, the suction and blow-off direction is crucial for performance.
Which air purifier or even air disinfection device is now the best, everyone must decide for themselves and their situation. It is indisputable that all devices filter or even eliminate germs from the air, only with different degrees of efficiency and different methods and technologies. This has been repeatedly proven with countless tests and studies, such as those conducted by the Fraunhofer Institute (1) or Stiftung Warentest (2), including during the last three Covid years.
The Fraunhofer Institute for Building Physics (IBP), for example, tested various ventilation systems in cooperation with the Bavarian Hotel and Restaurant Association and the VBW - Association of Bavarian Business. The results showed that all technologies were effective and the risk of infection could be noticeably reduced by reducing the viral load. Depending on the technology, up to 99 percent lower virus concentrations were achieved when the air purifier was operated for two hours. To assist the hospitality industry, an additional room air configurator [https://reineluft.darfichrein.de/home#get-started] was developed that allows establishments to receive individual recommendations for the best technology under their own requirements. (2)
A study conducted by the University of the German Federal Armed Forces in Munich also showed that it is possible to keep aerosol concentrations in small and medium-sized rooms at a low level without any problems within a relatively short period of time using air filter units. According to the research team, from their point of view, room air cleaners with a high-volume flow and high-quality filters of class H14 represent a very useful technical solution to greatly reduce the indirect risk of infection by aerosols in schools, offices, stores, waiting rooms, community and club houses, recreation rooms, dining rooms, etc. However, they can also be used in a supportive manner in buildings with ventilation or air conditioning systems, for example in waiting areas, open-plan offices or even gyms. (4)
It is important to know, however, that no air disinfection device succeeds in bringing the germ count permanently to zero if there is an infected person in the room. However, mobile devices can significantly reduce the concentration of infectious aerosols and thus the risk of infection.
Purchase criteria for room air purifiers
It is very individual what to look for when buying a room air purifier. In any case, these points should be included in the decision-making process:
Where will the air purifier be used - for example, individual or open-plan office, bedroom or living room?
How large is the room?
How many people are staying there?
Should it be permanently installed or flexible?
What do I want to achieve - disinfection, filtering allergens or eliminating odors?
How fast should the air be filtered or disinfected - keyword air circulation rate?
Is there already a ventilation system that can incorporate filters or disinfection technology?
And, not to forget, what budget is available? In addition, you should also pay attention to how high the noise level of the device is. After all, an air filter in the home or office should not disturb the normal daily routine.
Therefore, an air purifier for use in the office or at home should not be louder than a standard fan. As a small orientation - 35 to 38 decibels correspond to a light rustling of leaves and 42 to 46 decibels to quiet noises in the apartment, such as the dishwasher 10 meters away or the washing machine in the next room. You can get used to these noises and you won't really notice them after a short time.
Regardless of which air purification device is used, the first recommendation of the Federal Environment Agency to get rid of unwanted particles, odors and germs is still to ventilate. (5) This not only drives out germs, but also carbon dioxide, which we constantly exhale. Regular shock ventilation in combination with a suitable air purifier is therefore the best way to stay healthy.
Ventilation plus filtering protects best. The graph shows - depending on the behavior of those present - the number of viruses in a 16-square-meter, 2.5-meter-high room in which there is also a highly contagious person: Without ventilation and air filters, the virus load in the room increases steadily. If the room is aired for five minutes every 20 minutes, the number of viruses drops, but then rises again until the next airing. The number of viruses remains permanently low with ventilation plus the use of an effective air purifier. © Stiftung Warentest
We at UVIS are specialized in the technologies for disinfection of air. In our portfolio you will find various products that work with UVC or plasma technology. If you have questions about room air purifiers with plasma technology or UVC air disinfection devices and need help deciding on the right device, we will be happy to advise you.
Fotocredit: Hundt Consult, Stiftung Warentest
Published: 22. December 2022