We know of the novel coronavirus that it is transmitted through infected droplets emitted by sick people when they speak, sneeze or cough. If these infected droplets reach other people's mucous membranes, they can become infected. We also know that, to avoid infection, we must put in place very strict rules of behavior, such as maintaining the safety distance between people of at least one meter, preferably two or six feet, covering nose and mouth while coughing or sneezing with a handkerchief that then should be thrown away immediately or, where it is required, going out with a mask, not bringing dirty hands on your face, washing your hands frequently with soap and water for a minute and disinfecting hands and surfaces with solutions that contain at least 60% of alcohol. And as for indoor air, what happens if air conditioning is working? How can we improve the air in our houses?
Coronavirus, is air conditioning a risk?
Many are asking this question as a consequence of a study published a few days ago in the journal Emerging infectious diseases (Lu et al, April 2020). The study reports the cases of infection observed in a restaurant in Guangzhou, China. The restaurant is windowless and has air conditioning. The outbreaks have occurred between people who had lunch at different but close tables, about 1 meter away. The researchers came to the conclusion that the strong flow of air propagated by the air conditioning was the cause of the infection by transporting the infected saliva droplets from a person, infected with coronavirus, to the others. The study, as noted by the scientists themselves, has limitations, in fact it reports observations and not the result of a simulation. However, it should be considered relevant. It is clear that, in a house where there are no people infected, air conditioning is absolutely not a risk but attention must be paid in case of a positive person to coronavirus, but also in offices or other closed environments. Let's see what scientists and government guidelines recommend.
Coronavirus, how to improve indoor air
It is important to aerate the rooms often by letting in air from outside. The exchange of air in fact dilutes the virus. This can be seen precisely from a study published in the journal JAMA (Ong et al, 2020) in which it was observed that inside a room occupied by a patient with coronavirus the samples taken from surfaces were contaminated as well as air vents, while samples of the indoor air did not present the virus. The explanation is that the flow of air had diluted the virus to the point that it was not present in the air. Then, if in houses or offices a ventilation system is working, it is important to block any air recycling circuit to privilege only the introduction of air from the outside, in this way we guarantee a change of air in closed environments.
Coronavirus, maintenance of ventilation systems
As recommended by the guidelines of WHO and governments, it is good to regularly clean the air vents and grills of the air conditioners with a cloth soaked with soap and water or with 75% ethyl alcohol. During this operation, wear gloves and a mask and then wash your hands thoroughly with soap and water for a minute and/or disinfect your hands with a solution of water and alcohol of at least 60%.