Coronavirus in schools: Air purifiers alone are not enough – room ventilation is still key

Indoor Air Hygiene Commission takes stand on air purifiers at schools

Schülerinnen und Schüler melden sich.Click to enlarge
Pupils in an elementary school.
Source: iStockphoto / Wavebreakmedia

The use of mobile air purifiers alone is no substitute for adequate ventilation in schools. Mobile air purifiers merely circulate the air in the room and do not replace the necessary supply of outside air. However, there are cases where air purifiers can supplement ventilation in a meaningful way. This is the conclusion of a recent statement by the Indoor Air Hygiene Commission (IRK) at the German Environment Agency (UBA). The Commission recommends the use of air purifiers in schools where windows cannot be opened properly and where there are no simple supporting inlet and exhaust air systems. However, the devices should be properly assessed before use to ensure that they are suitable for the room in question. For example, the airflow rate must be high enough, the unit should not be noisy and should not emit any undesired pollutants.

In order to keep the risk of infection with the SARS-CoV-2 virus as low as possible, the IRK continues to recommend ventilation via wide open windows as the first and most important measure, in accordance with the German Environment Agency's guidelines of 15 October 2020. The guidelines state that ventilation should take place every 20 minutes for about 3-5 minutes and should be continuous during class breaks. If the windows cannot be opened wide enough, the second option is to install simple inlet and exhaust air systems in the windows. Such systems can remain in place beyond the pandemic and continuously improve the indoor air quality if ventilation is insufficient.

Only if these two options are not feasible does the IRK consider air purifiers to be suitable as a flanking measure to reduce the risk of infection. Their ability to reliably remove virus-laden particles in actual indoor spaces should be demonstrated through experimentation prior to use. The IRK stresses again that the use of these devices does not remove all impurities from the air in the room. Mobile air purifiers only circulate the air and do not replace the necessary supply of outside air. Therefore, every ventilation possibility should continue to be used even when using air purifiers.

The IRK states that rooms in which there is no possibility of ventilation via windows and where no ventilation system with a supply of outside air is used are not suited for teaching purposes.

According to the IRK, all the measures, ventilation plans and techniques mentioned here and, if necessary, the use of mobile air purifiers do not replace the other protective measures against SARS-CoV-2. In particular, they do not provide effective protection against exposure through direct contact or droplet infection at short distances. Compliance with the basic safety rules (keeping a distance, hygiene/hand washing, wearing a face covering) must therefore continue to be observed regardless of the above measures.