Corona virus: infection by air conditioning and ventilation?

They provide fresh air and are ubiquitous in many buildings: Ventilation and air conditioning systems not only cool the rooms, but also introduce fresh air into the rooms. But is there a dangerous virus launcher hidden here? To what extent can coronavirus be distributed through air conditioning and ventilation? Researchers have been concerned about this for quite some time.

Can air conditioners expel the corona virus through the room and into our lungs?

They were sometimes the first bad headlines when the Sars-CoV-2 coronavirus was just beginning to make its way around the world: infected on cruise ships, entire crews, and quarantined passengers, nowhere to get permission. In many cases, passengers were supposed to spend weeks in their cabins, they were supplied from outside. And yet, the cruises turned out to be true incubators for the virus. Many people fell ill, but how exactly?

A similar situation arose in late January at a restaurant in Guangzhou, China. In a multi-story but windowless restaurant, three families sit at different tables, otherwise without contact. Soon after, Covid-19 was detected in ten people from these three families. The assumption: the virus was supposed to be from a single infected person in the restaurant, and nine other people were infected with the coronavirus there; This shows a reconstruction of the transmission routes that the researchers had carried out.

Since the families are said to have had no contact with each other, the researchers suspect that the air conditioning system played a role in the transmission of the virus.

Air conditioning hazard factor: How big is the hazard really?

Scientists’ Assumption: Airflow from the air conditioning system carried viruses much further than when talking, coughing, or even sneezing. They therefore call for the distance between the tables to be increased and for air conditioning systems to be better controlled and for external ventilation to be improved.

But the epidemiologist Rafael Mikolajczyk from the University of Halle takes a little fear of air conditioning, writes “sueddeutsche.de”: It is not so early to conclude from this Chinese study that all ventilation systems are dangerous. “There are technical differences in air conditioning systems and the possibility of filtering, all of which must be considered,” explains the expert.

“With the coronavirus, we are more likely to assume a droplet infection, where transmission occurs in the immediate vicinity rather than through aerosols that are transported over longer distances.” This also coincides with the statements made by the virologist Charité Christian Drosten. Studies have shown that that in a kind of aerosol, even infectious viruses can stay in the air for hours. However, the viral load, that is, the amount of virus in the air, appears to be so low that it is difficult for people to become so infected; this needs further investigation.

Good room ventilation reduces the risk of infection.

Instead, experts agree that good room ventilation helps reduce the risk of infection. Of course, this mostly means going through open windows. But air conditioning systems can also make a huge contribution to ventilation here, provided they transport fresh air and not just allow the air in the stale room to circulate. The researchers assume that many people were infected in a bar in Ischgl, Austria, or in a club in Berlin, for example, because there was hardly any fresh air supply in the rooms and there was only poor ventilation.

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The Federal Environment Agency (UBA) also confirms that it depends on the type of air conditioning and its maintenance interval: on cruise ships, for example, it is common that the exhaust air from the interior is not completely emitted to the outside through systems central ventilation but to some extent continue indoors to circulate Viruses could well spread. This would also explain why so many people could become infected on cruise ships, such as the stranded Diamond Princess of Japan. A similar phenomenon occurred in 2002/03 when Sars (Sars-CoV-1) erupted in a Hong Kong apartment block where several hundred residents may have been infected due to a faulty exhaust system.

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For air conditioning: check correct operation!

According to the UBA, incorrect planning and poor maintenance could lead to “incorrect flows”, for example, if the exhaust air from one part of the building does not go outside as planned, but to another interior area. “In such cases, the spread of viruses through the air conditioning system cannot be ruled out,” says UBA.

Air conditioning systems that ventilate only one room and are serviced regularly, the function of which is therefore confirmed, pose no danger. So there is no increased risk of infection with the Corona virus