When a person with coronavirus coughs, talks or sneezes, a stream of droplets and aerosols of different sizes is generated, which enters the ambient air and spreads. All these different-sized droplets and aerosols potentially contain viruses. <\/p>\n\n
As we saw earlier, viruses spread via micro-droplets and aerosols generated when people talk, cough or sneeze. People on company premises can easily generate them when talking to each other or on the phone, for example. Viruses become airborne, carried by aerosols, and can come into contact with other people. If these aerosol particles are inhaled in sufficient concentration, people can become contaminated. The louder people speak, the more aerosols float in the air. <\/p>\n\n
Ventilation improves air exchange in the room, reducing the risk of transmission. Fresh outdoor air disperses aerosols, indoor air is diluted and contamination is less likely. According to a Japanese study, we are 18.7 times more likely to be infected indoors than outdoors. <\/p>\n\n
Room ventilation is also useful for other illnesses such as influenza or flu-like infections. The provision of fresh air is therefore crucial. Untreated air-conditioning systems that simply stir the air in the room should be avoided. <\/p>\n\n
According to current knowledge, coronavirus transmission via ventilation and air-conditioning systems can be ruled out if these are fitted with integrated high-efficiency HEPA H13 filtration. This is because viruses are transmitted by droplets. Thanks to the built-in filters, and if they are of sufficient quality, no droplets (which could contain the virus) can enter the rooms. What’s more, because of the increased air exchange, the number of particles in the room is significantly lower. It should be noted that if the existing air handling system is not equipped with filters, or if these filters are insufficiently efficient (of the G4 or F7 type, for example), it is often difficult to improve the filtration efficiency of the installation without significantly degrading the flow rate. In this case, it may be useful to add an ambient air purification system as a complement. <\/p>\n\n
Many older air-conditioning systems are often used as recirculation systems to save energy. This means that some of the exhaust air is mixed with some of the outside air and returned to the room. In the current pandemic situation, it is recommended to avoid the use of recirculated air and to prefer “all fresh air” if the air is not treated with high-efficiency HEPA filtration. In practice, this is achieved by closing the air recirculation dampers. <\/p>\n\n
The question is often asked whether existing filters in air-conditioning systems should be upgraded with more efficient filters. In most cases, improving the quality of filters in existing air-conditioning systems is not possible because the available pressure is too low. Adding filters of a higher class (HEPA) would significantly degrade air-conditioning output. <\/p>\n\n
Aerosols in indoor air contribute to the spread of coronavirus. Tiny droplets can remain in the air for hours, causing infection even if the infected person has already left the room. <\/p>\n\n
An air purifier reduces the concentration of viruses and germs, and of course other pollutants such as dust, pollen and allergens in indoor air. In this way, they can also help to significantly reduce the concentration of the current coronavirus in ambient air. <\/p>\n\n
It makes sense to use air purifiers with H13 or H14 HEPA filters for viruses and germs<\/a>. These have a permeability of 0.005% and should be used to remove pollutants from the air, particularly in high-traffic areas such as waiting rooms in doctors’ surgeries, offices, schools<\/a>, canteens or production plants. Air purifiers with HEPA H14 filters are also used in hospitals and laboratories. <\/p>\n\n