When a person infected with Covid-19 speaks, coughs or sneezes, it emits infectious droplets that can settle on surfaces and fine particles that remain suspended in the air. Should we be afraid of the air conditioning? Are the risks the same depending on the means of transport? In company ? At home ?

Does air conditioning have a role in the spread of Covid-19? Thanks to summer, many of us are asking ourselves this question. At the end of April, a Chinese study published in the Emerging Infectious Disease newsletter raised the alarm. A customer positive for the coronavirus and installed in the air conditioning of a restaurant in Canton would have infected 9 other people who were around him at lunch time.

What are the risks according to the different types of places? Insights from Dr Fabien Squinazi, medical biologist.

What are the risks on board a train?

The air filtration system is not very high efficiency. “It retains the large droplets but not the fine ones. The blown air circulating in the wagons can therefore disperse small suspended viral particles, "explains Dr Fabien Squinazi.

What are the risks on board an airplane?

"The air is purified by very high efficiency filters (HEPA) which stop viral particles," says the specialist. However, it remains possible to be contaminated in an airplane, not because of the ventilated air, but because of the proximity to a passenger carrying the virus or of contact with a soiled surface, the hands remaining a mode of protection. significant transmission of the virus.

What are the risks in the bus or the metro?

The risk of transmission is low, according to Dr. Squinazi, because the air taken in from the outside is naturally renewed by frequently opening the doors. "This supply of fresh air dilutes the pollutants and germs inside the bus or metro, and virus particles emitted by an infectious passenger will be more easily eliminated. "If we can open the windows, that's even better.

What are the risks in a department store?

Modern collective installations are equipped with an air handling unit that does not mix the fresh air that it blows into the premises and the blown air that it recovers. It therefore does not promote the transmission of viral particles if it is well maintained and perfectly sealed between the two air circuits.

At home, can air conditioning spread coronavirus?

An individual air conditioner circulates the air in the room, it does not renew it. It will therefore mix the viruses with the air in the room and then put them back into circulation. “An air conditioner can project the droplets emitted by breathing, speaking, coughing or sneezing farther away. Therefore, avoid airflow directed towards the face, ”recommends Dr. Squinazi.

If the air conditioning is collective, it does not spread germs in the air of the room. But if the installation is individual, it promotes the mixing of viral particles in the air.

The importance of barrier gestures and physical distancing

On the train and on the plane, take all the barrier measures: wear a mask, respect physical distancing and rub your hands as often as necessary with hydro-alcoholic gel.