Under the current guidelines, classrooms should be cross-ventilated or have their windows fully opened for five minutes every 20 minutes. Air purifiers can be used to complement window ventilation in buildings where these measures cannot be implemented. A new study by the Steinbeis Virtual Testing Research Centre simulated how air purifiers affect aerosol concentration levels in classrooms and validated the data using on-site readings from a professional appliance manufactured by WOLF GmbH. The study showed that the AirPurifier was effective at reducing aerosol concentration levels throughout the room during the ventilation break and significantly reduced the concentration of infectious particles.
Real-world data confirms the effectiveness of professional air purifiers
“We ran a comprehensive flow distribution simulation and checked the results against real-world measurements taken in a classroom. Both datasets show that the air purifier is very effective at filtering the air throughout the room. The purifier lowered the concentration of a test aerosol by 80 percent on average within 30 minutes; in certain locations, concentration levels were 90 percent lower,” explained Prof. Uwe Janoske, Head of the Steinbeis Virtual Testing Research Centre.
The simulation and real-world measurements used a WOLF GmbH AirPurifier, currently in use at the Johannes Nepomuk Gymnasium school in Rohr in Niederbayern, Germany. Air purifiers are normally tested using a simulation-based approach. WOLF GmbH wanted the Steinbeis Research Centre to take real-world measurements of aerosol concentration levels as well.
A test aerosol was evenly distributed around a classroom before taking measurements during six lessons and outside of school hours. Researchers used an optical aerosol spectrometer to monitor changes in the number of particles over time at six locations around the 64 m2 classroom. Concentration levels went down significantly at all of the locations with the windows closed under both real-world and test conditions. The AirPurifier reduced particle concentration by an average of 80 percent within 30 minutes. These measurements were in line with the simulation. The flow rate of the AirPurifier was set to 1200 m³/h during the test. This flow rate provides effective filtration for a room of this size.
Air purifiers are becoming more popular, particularly as school infection rates continue to rise. A major study from three Austrian universities recently concluded that schools are a significant transmission location for COVID-19. Children are less likely to develop symptoms but remain capable of infecting others.
Quiet air purifiers for concentration and uninterrupted lessons
This appliance has a sound pressure level of just 34 dB(A) in normal operation, making it perfectly suited for a classroom. A WOLF AirPurifier was installed in the year 8 classroom at the Johannes Nepomuk Gymnasium in Rohr in mid-October. None of the 18 pupils or their teachers reported any issues with the appliance. In fact, they have barely noticed the air purifier at all because of how quiet and reliable it has been.
They also found the presence detection system and run-on time feature very useful, as it prevents the appliance from running at night or at weekends when it is not needed. “We were a bit unsure about it at first, but the appliance is now an integral part of the classroom,” explained Carola Reim, Director of the Johannes Nepomuk Gymnasium. “The WOLF AirPurifier is providing our pupils and teachers with extra protection against viruses and bacteria during the pandemic. It also makes it easier for us to keep the classroom hygienic when it’s cold outside.”
Efficiency of WOLF AirPurifier scientifically confirmed
Tests performed by the hygiene institute biotec GmbH confirmed that the WOLF AirPurifier was effective at reducing airborne viruses. The 99.995% efficiency rating of the DIN EN 1822 certified HEPA H14 filter is applicable to the entire air purifier. This efficiency rating was tested using MS2 as a surrogate virus for SARS-CoV-2 in a single pass through the filter. The WOLF AirPurifier is therefore scientifically proven to remove potentially infectious aerosols from the air.
“The studies conducted by the Steinbeis Virtual Testing Research Centre and biotec GmbH show that the WOLF AirPurifier is effective at removing aerosols in real-world situations. It is clear that professional air purifiers are particularly helpful in situations where window ventilation on its own will not be enough. They are no replacement for effective ventilation; however, they are effective at quickly reducing the impact of inadequate ventilation. A long-term solution would be an air handling unit which uses 100% fresh outdoor air, while also allowing you to control temperature and air humidity levels,” said Dr. Thomas Kneip, Chairman of the Management Board of WOLF GmbH.
More information about the AirPurifier can be found here: