Many stores cool mainly with recirculating air conditioners. This can promote the spread of coronaviruses.

The popular recirculating air conditioners are a problem - because of the corona virus. They suck in the room air and blow it out again cooled. So the same air is always circulating in the room. In closed rooms with several people and no fresh air supply, this increases the risk of corona infection through aerosols, says Walter Zingg, specialist for infection prevention and hospital hygiene at the University Hospital of Geneva. In addition, "a recirculating air-conditioning unit that does not clean the air and tends to dry it out, which also cools the air - these are all factors that further promote aerosol transmission." 

The Federal Office of Public Health also says that air conditioning systems should be operated with a high fresh air exchange rate and as little recirculated air as possible for good protection against viruses. For this reason, the Swiss building technology association Suissetec has also been recommending that its members no longer operate recirculating air conditioning units since the lockdown.

Unhealthy air conditioners run everywhere

But what does it look like in practice? Are Suissetec's recommendations actually being implemented in stores to protect customers and especially staff? "Kassensturz" visited various stores and supermarkets in Switzerland together with the independent ventilation expert Christian Stäuble. The specialist examined the ventilation system in each case.

What he observed during the random sample is worrying: there is 100 percent pure fresh air in none of the stores visited. On the contrary: all of them are air-conditioned with recirculation units, the air is not filtered at all or only slightly, and the proportion of fresh air is minimal. Christian Stäuble is surprised: "Sure, these recirculation units have been in place for a long time and nothing could be done in this short time. Nevertheless, it is disturbing that they are still in operation everywhere."

The stores and supermarkets write "Kassensturz" that they have good protection concepts and comply with the applicable legal requirements. So far, there have been no known cases of infection via aerosols in the stores. The pharmacy also emphasizes that none of its employees has been infected to date. An infection through coronaviruses via the air seems unlikely here.

Danger could be contained with simple measures

Nevertheless: Better and cleaner air in stores and generally in closed rooms would be possible. The risk of infection could be contained with simple measures. For example, with a UV-C device. It also works according to the recirculation principle, but has a crucial addition. Ventilation expert Christian Stäuble explains: "The air drawn in flows through special tubes that emit nanoscale waves. These kill viruses and bacteria." The air thus flows back into the room in a purified state.

Walter Zingg, member of Task Force Covid-19, confirms the effectiveness of these tubes: "The UV-C mechanism for killing bacteria and viruses is proven. There are enough studies that have proven in laboratory tests that this is useful. This is not mumbo jumbo." Adds that such UV-C tubes could also be retrofitted into existing ventilation systems. Relatively simple and inexpensive.

But the stores see no need for action. Not yet. Yet there would still be plenty of time now, before the next flu season.

Source: Kassensturz, published on 25.08.2020