Since it has been known that the corona virus can also be passed on via the indoor air, mobile air purifiers have been very popular. For a few thousand euros, restaurateurs and organizers, but also private individuals or schools can buy such a box. The manufacturers promise that the devices will almost completely filter out infectious aerosols from the room air. As an alternative to school lessons with an open window in freezing temperatures, that sounds like a good idea.
But do the devices keep what they promise? Researchers at the Goethe University Frankfurt have put the test to the test. Joachim Curtius, Professor of Experimental Atmospheric Research, and his team set up four air purifiers for a week in a school class with teachers and 27 students. The air purifiers had a simple pre-filter for coarse dust and lint as well as a HEPA filter of class H13 and an activated carbon filter.
The bottom line: certain air purifiers can reduce the aerosol concentration in a classroom by 90 percent in half an hour. “An air purifier reduces the amount of aerosols so much that in a closed room the risk of infection from a highly infectious person, a super-spreader, would be reduced very significantly,” said Curtius after a model calculation based on the measurement data.
The University of the Federal Armed Forces in Munich came to a similar conclusion. The team around Christian Kähler from the Institute for Fluid Mechanics and Aerodynamics has tested room air purifiers with large volume flow and high-quality filters of class H14. The device therefore had a filter combination that ensures that 99.995 percent of aerosol particles with a diameter of 0.1 to 0.3 micrometers are separated from the room air.
“The results show that the aerosol concentration in a room with a size of 80 square meters can be reduced to a low level within a short period of time”, write the authors of the analysis. They are “a very useful technical solution” to “greatly reduce” the risk of infection from aerosols.
Different filter classes
However, if you are thinking of purchasing such a device, you have to look carefully. “There are different filter classes,” explains Martin Kriegel, aerosol researcher and head of the Hermann Rietschel Institute at the TU Berlin. “The classic way of installing fine dust filters in ventilation systems is to separate around 50 percent of the aerosols.” Higher quality filters – Kriegel calls H13, H14 or ULPA – work so well, in his opinion, “that the filtered air is considered particle-free”.
Hesse’s state government has already announced that it will support the school authorities with ten million euros in the purchase of air cleaning devices. “These are to be purchased especially for classrooms where it is not possible to ventilate adequately, for example because windows cannot be opened,” said Minister of Education Alexander Lorz (CDU).
“Classic ventilation more effective”
The Federal Environment Agency sees the issue more critically. The Office’s Indoor Air Hygiene Commission advises classic ventilation: “The highest possible supply of fresh air is one of the most effective methods of removing aerosols from indoor spaces that contain viruses,” according to a detailed statement. Mobile air purifiers in classrooms or at home could “not replace active ventilation, but rather supplement it in individual cases”.
The consumer advice centers also warn against blindly trusting the promises made by manufacturers. You can do a lot wrong when buying. For example, the cleaning performance must match the size of the room and the number of people, and the filters must be changed regularly. In addition to the filter performance, some manufacturers advertise additional measures against viruses, such as ozone or UV light. The Federal Environment Agency advises against such devices “for health reasons as well as for safety reasons”.
The Sars-CoV-2 virus can be inactivated with ultraviolet light – this is shown, among other things, by a study by the Essen University Medical Center. For example, medical equipment can be decontaminated with UV-C lamps. But the Federal Office for Radiation Protection warns: “Since UV radiation can damage the skin and eyes and has been proven to be carcinogenic, UV-C disinfection devices should only be used in such a way that no people are exposed to the radiation.”
Some cities still rely on this technology, such as Hanau in Hesse. In August, the city concluded a “strategic partnership” with a local company that uses UV-C rays for disinfection. The devices suck in air, sterilize it by means of radiation and release it back into the room. The provider emphasizes that the devices are designed in such a way that neither ozone nor radiation is released.
Meanwhile, alternative cleaning techniques are still being sought. For example, two Fraunhofer institutes (IKTS and ITEM) are working on a new system to disinfect the air in closed rooms. With total electrochemical oxidation, organic substances such as viruses are completely destroyed. “After successful development of a prototype”, according to the institutes, “the market launch should be pushed ahead as soon as possible”.
(WHAT / dpa)
*We just want readers to access information more quickly and easily with other multilingual content, instead of information only available in a certain language.
*We always respect the copyright of the content of the author and always include the original link of the source article.If the author disagrees, just leave the report below the article, the article will be edited or deleted at the request of the author. Thanks very much! Best regards!
These were the details of the news What do air purifiers bring in the fight against corona? for this day. We hope that we have succeeded by giving you the full details and information. To follow all our news, you can subscribe to the alerts system or to one of our different systems to provide you with all that is new.
It is also worth noting that the original news has been published and is available at en24news and the editorial team at AlKhaleej Today has confirmed it and it has been modified, and it may have been completely transferred or quoted from it and you can read and follow this news from its main source.