To fight the Covid, open windows at least five minutes every hour

Open windows for at least five minutes every hour in places open to the public to better fight Covid-19: this is what the High Council for Public Health (HCSP) recommends in a notice made public on Monday 3 May.

For this body, whose role is advisory, the “Control of aeration-ventilation” establishments open to the public must constitute a “Strong point” on which a health protocol can be based. This is all the more true “When certain barrier measures (in particular the mask or the distance between individuals) are not adapted to the activity of the establishment”, like kindergartens or restaurants.

Many scientists insist on the importance of ventilation to fight the spread of Covid-19. We know, in fact, that the disease is transmitted a lot via aerosols, clouds of droplets produced by the breathing, speaking or screaming of infected people that contain SARS-CoV-2. These clouds can remain in suspension for several hours, hence the importance of good ventilation to disperse them.

CO sensors₂

“In schools and universities in particular, it is proposed to leave doors and windows open between lessons and lessons”, writes the HCSP in its review. According to him, “Only windows should remain open during lessons or lessons”, the ideal being“Open two windows, if possible, to promote air circulation”.

In situations where ventilation is not possible or insufficient (windows blocked), ” technical solutions must be put in place (eg flaps or ventilators in the upper part of the windows, forced ventilation, etc.) ‘, specifies the instance. In this case, the HCSP considers that “The reduction in the occupancy rate of the premises can then contribute to obtaining satisfactory air quality”.

To better assess air renewal, the HCSP recommends measuring “The concentration of carbon dioxide at representative points and periods during a period of occupation”, thanks to CO sensors₂.

“A CO concentration₂ above a threshold of 800 ppm [“partie par million”, unité de mesure du taux de pollution dans l’air] must lead in all cases not to occupy the room and to act in terms of ventilation-air renewal and / or reduction of the number of people admitted to the premises ”, he concludes.