Can air conditioning facilitate the propagation of coronavirus? This is the question scientists from the Guangzhou center for disease control and prevention tried to answer back to late April 2020. Their study was focusing on a particular case, that broke out in a Canton restaurant, China, where all patrons have been infected by Covid-19 without previous contamination signs. Results supported early July by several scientists saying air conditioning could be partly responsible for the resurgence of cases in the United-States.
“The states that, in June, are already using a lot of air conditioning because of high temperatures are also the places where there’s been greater increases in spread of COVID-19” Edward Nardell, professor of medicine and of global health and social medicine at Harvard Medical School. He goes on: “hot summer temperatures can create situations similar to those in winter, when respiratory ailments tend to surge, driving people indoors to breathe — and rebreathe —air that typically is little refreshed from outside”. Results that are also listed by the WHO in their latest public statement on July 7, 2020 explaining the “epidemic was speeding up”.
Coming back to the Chinese study, it told us in late April that every patron in the restaurant has been infected by one person showing no symptom of the disease. In concrete words, that person only could have not only contaminated their family there on that day, but also all people at the tables around them. If the first analysis seems logical, we can wonder about the nature of the contamination of other people, yet seated far from the patron carrying the virus.
According to the Chinese scientists, the airing system of the restaurant is at the origin of the phenomenon. The air conditioning, which “airflow direction” could be the “key factor for infection”. An analysis that supports the scenario of an airborne transmission of the virus. It seems clear that these ultra-fine particles we spread simply when talking or breathing could cause such a situation.
As we can see on the study’s explicative sketch, the air blown by the contaminated case seated at the table A went into the air conditioning system, and was then spread across the room. We understand that the air conditioning orientation helped the spread of these micro-particles towards these people.
Moreover, searchers say that air-conditioning itself is not helping the spread of Covid-19, but its misuse. Their conclusions are clear: when air conditioning processes the air from outside, to spread it inside, it becomes an excellent way to recycle the contaminated air inside. It also shows the air from the outside could enable the dilution of aerosols filled with virus on the condition they do not make the air circulate again to zones that are not contaminated. In the case of the restaurant, the “inner” misuse has caused the chain contamination.
The same way a car air conditioning system protecting you from the outdoor pollution, the question of the use of the air conditioning system to fight the coronavirus remains very tight to searches on the capacity of the virus to stay in the air, still not conclusive today. So far, there is nothing sure about its lifespan or its infectious character. Anyway, if you happen to have an air conditioning system, we recommend you always create a flow towards the outside. Or open the windows regularly to manually air the room.