Reduce the risk of infection: air purifiers against aerosols
It has long been known that the novel coronavirus SARS-CoV-2 is spread not only through droplet infection, but the so-called aerosols can play a role in infection as well. A study has now shown that room air filters can remove a large part of these particles – in just 30 minutes.
A research team has found that air filters can reduce the concentration of aerosols in a classroom by 90% in half an hour. (Image: Dmitry Vereshchagin / stock.adobe.com)
According to a recent press release, researchers at Goethe University in Frankfurt found that air purifiers of the HEPA (H13) filter class can reduce the concentration of aerosols in a classroom by 90% in one half an hour. The study was published on the “medRxiv” pre-print server before being published in a scientific journal.
Reduce the aerosol concentration in a room
The most dangerous route of infection for the SARS-CoV-2 coronavirus is through the air: when sneezing or coughing, for example, infected people throw out relatively large droplets, which, however, sink into the body. ground within a radius of two meters.
But aerosol particles are also important, much smaller droplets of liquid that we also secrete when we speak or breathe. Studies have shown that infectious SARS-CoV-2 viruses can still be detected in these aerosols more than three hours after emission and can be found several meters from patients.
The liquid in these aerosol particles evaporates quickly, making them smaller and allowing them to spread around a room within minutes. It also increases the risk of infection and additional safety measures are needed.
Due to the buildup and distribution of aerosols in the room, maintaining the minimum distance for infection prevention may no longer be sufficient, writes the Robert Koch Institute (RKI). Efficient air exchange can reduce the concentration of aerosols in a room. Air filters also promise help in the fight against polluted indoor air.
Extraordinary results after just 30 minutes
Joachim Curtius, professor of experimental atmospheric research at Goethe University in Frankfurt, and his research team spent a week testing four air purifiers in a school classroom with teachers and 27 students.
The devices had a simple pre-filter for coarse dust and lint as well as a HEPA filter and an activated carbon filter. According to reports, air purifiers together convert between 760 and 1,460 cubic meters of air per hour.
In addition to aerosol pollution, scientists determined the amount of fine dust and CO2 concentration and examined the noise pollution from devices. The result: half an hour after it was turned on, the air purifier had removed 90% of aerosols from the air.
Significantly reduced risk of infection
“Based on our measurement data, we made a computational model that can be used to estimate: an air purifier reduces the amount of aerosols so much that the risk of infection from a highly infectious person, a super spreader, would be very significantly reduced in a closed room “, explains Professor Curtius.
“That’s why we recommend that schools this winter use HEPA air purifiers with a sufficiently high air flow.” Noise measurements and a survey of study participants showed that noise from the air purifier was generally not seen as bothersome unless the device was at the highest level run.
In addition to the risk of infection, the air purifier also reduced pollution from allergens and fine dust, as the researchers measured.
“However, an air filter does not replace the regular opening of the window, which again reduces the concentration of CO2 in the room. Our measurements in the classrooms showed that the values were often higher than the recommended limit values. We recommend installing CO2 sensors here so that students and teachers can check this, ”says Joachim Curtius. (a d)
Author and source information
This text conforms to the requirements of specialized medical literature, medical directives and current studies and has been verified by health professionals.
Goethe University Frankfurt: Risk of infection: Air purifiers remove 90% of aerosols in school classrooms, (accessed October 6, 2020), Goethe University Frankfurt Joachim Curtius, Manuel Granzin, Jann Schrod: Testing air purifiers ‘air mobiles in a classroom: Reducing the risk of airborne transmission for SARS – CoV – 2: Preprint: medRxiv, (published: October 5, 2020), medRxivRobert Koch Institute: SARS-CoV-2 Profile on Coronavirus Disease-2019 ( COVID-19), (accessed October 6, 2020), Robert Koch Institute
This article is provided for informational purposes only and is not intended to be used for self-diagnosis or self-treatment. It cannot replace a visit to the doctor.