German testing foundation “Stiftung Warentest” recently tested three of its air purifier test winners for a second time. This time, the effectiveness in removing aerosols was to be measured in particular. For this purpose, different particle sizes, including those of individual coronaviruses, were introduced into the room air for the investigation. The models tested were small, mobile air purifiers in the household class around 400 EUR, with a filter class far below HEPA H13, the minimum standard for professional air purifiers.
Drop in performance after just a few months
In the first runs, the devices performed well: after 20 minutes, they had filtered out over 90 percent of the particles in a room of 16 square meters. But after several (simulated) months of use, the performance curve dropped off rapidly in some cases, as Reiner Metzger, editor at Stiftung Warentest told Der Spiegel. One device filtered only just under 50 percent of aerosol particles from the air, although a filter change was far from indicated. Metzger recommends considering exactly what type of room the device should be suitable for before buying an air purifier. How large is the room? How many people are staying here? For how long? For classrooms, a single one of the units tested is not sufficient, Metzger said.
The right air purifier
In highly frequented rooms such as classrooms, public buildings or stores, experts explicitly recommend the use of professional, powerful air purifiers with HEPA class H13 or higher. These devices, which include the AiroDoctor, can clean rooms of 200 square meters in just a few minutes – the substances filtered out include even the smallest particles such as individual coronaviruses or the somewhat larger infectious aerosols. The AiroDoctor is also unique in that it additionally and safely destroys the filtered-out particles using photocatalysis technology, rendering them harmless forever.
Avoid to buy twice
When choosing the right air purifier, it is also important to pay attention to the possible emission of harmful by-products such as ozone. Other criteria include low operating noise, low maintenance costs and easy and safe filter replacement. Therefore, when buying an air purifier, it is better to choose the right filter technology right from the start. Because here, too, the following applies: If you buy cheap, you buy expensive.