We have summarised below answers to the most pressing questions relating to air conditioning and ventilation.


Why have air conditioning systems for buildings become involved in the discussion about the spread of the coronavirus?

Cooling technology has been identified as a catalyst for the spread of the virus in processing plants in the meat industry and the ventilation system played a key role in an incident in Heinsberg. However, clarification is called for: when operated properly, air conditioning systems are generally harmless as a supply of fresh air is called for.

Why does the volume of fresh air play a key role?

Fresh air ensures that the concentration of the viruses in the air is reduced, as filtered, treated air is fed in and polluted indoor air is carried away. The proportion of fresh air in ventilation systems needs to be increased to the maximum in these times. Alternatively ventilation through windows also helps.

Why is air circulation of concern?

Air circulation indicates how many times each hour the air in the room is technically processed. A high rate of air circulation (around 20 or 30 times in meat processing plants) generates strong air turbulence, which keeps viruses on the move. However, two-fold air circulation is more usual when air conditioning an office or hotel bedroom. These air movements are so minimal that viruses become deposited on surfaces and quickly die off.

Is it possible to equip air conditioning systems with virus filters?

Retrofitting filters is not sensible as the relevant filters (HEPA) would have too serious an impact on the output of existing systems. In principle, it makes sense to purify the air in a separate unit that works independently of any air conditioning or ventilation technology. One example of this would be the KA-520 air purifier. This is the only way to achieve a meaningful combination of HEPA filter and fan unit. And only in this way can the expensive filter be used only when it is really needed.

Can recirculating air conditioning systems continue to be used?

Recirculating air systems, such as unit heaters, fan coils, ceiling cassettes or trench heating, can continue to be operated. They produce minimal air circulation, viruses can also deposit themselves and die off in the same way as they would were the system switched off. They do not transport the air across large distances and, above all, it is not transported from room to room (or section to section). Their installation and use is therefore harmless.

The German Professional Association for the Air Conditioning of Buildings also states that recirculation air units, such as fan coils or secondary air units, are “only effective in the respective individual unit in accordance with the regulations. They do not transfer the air into other units and are not therefore critical.” (Source: Operation of ventilation systems within the constraints of the current Covid-19 pandemic 24.04.2020, version 2)