Rooms: Potential hazards for direct or indirect infection
Viruses are primarily transmitted via droplets when people breathe, sneeze, speak, or cough, for example. Inside rooms, non-infected people can become infected over short distances (less than 1.5 m) by inhaling emitted droplets. This is called ‘direct infection’. Small droplets are also called ‘aerosol particles’. As they can float in the air for hours and even be transported across great distances, people can also become infected in rooms that infected persons have not occupied for hours. This is called ‘indirect infection’. In general, the risk of infection increases in rooms and the likelihood of infection in any given room increases with the number of infected persons occupying it and the length of their occupation. Many modern buildings use ventilation systems that discharge stale or contaminated air and feed in fresh air from outdoors. However, for energy reasons they are often only operated with single filters and a controlled fresh air supply, and must also be serviced at regular intervals. Due to moderate climatic conditions, buildings in most European countries are typically ventilated by allowing air to freely enter through open windows and doors. Depending on the wind’s speed and direction, window size, etc., the concentration of aerosols and pollutants can be quickly reduced by cross ventilation. However, when the windows are closed again the aerosol and pollutant content of the air continuously increases again. Many people find it impossible to cross ventilate at short intervals or permanently ventilate during the daily work routine, tilted windows do not lead to effective air exchange in rooms, and building ventilation systems cannot always be retrofitted or retrofits involve high costs. As a result, alternative solutions are in demand.
Air purifiers reduce the aerosol and pollutant concentration in rooms
According to a 2020 study by Universität der Bundeswehr München, powerful air purifiers can quickly reduce the aerosol concentration in small and medium-sized rooms to a low level and maintain it at that level. High-quality air purifiers with multi-stage filter systems and HEPA H14 filters ensure that 99.995% of aerosols and other pollutants such as particles with a diameter of 0.1 to 0.3 µm can be removed from the air in rooms. Of course they remove 100% of larger particles. Air purifiers ensure that viruses and other harmful substances are completely removed and cannot be redistributed in the building through other channels.
There are no alternatives to improved health protection
Alongside the health-related dimension, air purifiers go hand in hand with responsibility. Employers, works councils, in-house occupational health officers and others with responsibility for employees are well aware of health protection’s surge in importance during the coronavirus pandemic. They have already implemented many countermeasures, including the ability to work from home, providing FFP2 masks on company grounds, installation or modernisation of building ventilation systems, and setting up air purifiers in office and conference rooms. The economic aspects must also be considered. Many companies require work that can only be carried out by specific groups and persons. If such experts or entire departments are unable to work for longer periods due to illness or quarantine, economic losses may result. ‘Business as usual’ is certain to be different after the pandemic is under control. The changes we have had to make are too extensive and serious. With a view toward the possible risk of a new virus-driven pandemic in future, various measures must be taken right now to improve health protection.
What to consider before purchasing a mobile air purifier
The findings of the Universität der Bundeswehr München study indicated that a large volume flow and an optimal filter combination that includes a HEPA H14 filter are crucial factors for air purifier effectiveness. Where the air purifier will be used is a further point to consider. Air purifiers destined for operation in offices and other noise-sensitive environments must also be quiet.