VIDEO – Enclosed places ventilated enough? From the metro to the restaurant, the life-size test of TF1

They are at the heart of health protocols, especially in schools, sometimes coupled with air purifiers: CO2 sensors make it possible to measure the concentration of carbon dioxide in the air of a room. When many people concentrate in a confined space, whether they expire, speak or cough there, for example, this concentration increases, and with it the danger of seeing viral particles multiply. The risk of Covid-19 infection then increases. As soon as the CO2 rate is too high, the device therefore sends a signal to indicate that ventilation is required.

The alert threshold was set last May by the High Council for Public Health, which indicated on its website that a “CO2 concentration above a threshold of 800 ppm” indicates that the air in the room is not renewed enough, and “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 of an ERP (Establishment Receiving the Public, editor’s note )”.

But if the use of these devices is recommended in public spaces, it is not mandatory. In the case of primary schools, only 20% of them are equipped with them, affirmed on January 2 the Minister of Education Jean-Michel Blanquer in the columns of the Parisian, insisting on an envelope of 20 million euros released by the State to help communities to obtain it.

But what about other enclosed public places? In the video report at the top of this article, a team from TF1’s 20H took a portable sensor on board in several areas where there are high population concentrations. In many cases, the air becomes saturated very quickly and the risk of contamination skyrockets.

In restaurants first of all, the sensor quickly switches to red, which is all the more worrying since it is impossible to keep your mask on at the table, whereas this allows you to filter the air. TF1 journalist Mathilde Verron went to a Parisian fast-food restaurant where there were many customers and the windows were closed. The sensor then displays 1996 ppm, more than double the threshold recommended by scientists.

Even in an almost empty restaurant, the sensor gets carried away: it registers more than 1200 ppm. “You have to eat windows wide open, at zero degrees?”, quips a customer. “It’s impossible to hold, it’s completely mind-blowing”, plague another.

Outdoors, on the other hand, in the street, the lights are green. The sensor is at 400 ppm, half of the alert threshold. Transport, on the other hand, concentrates a lot of saturated air. In a crowded subway train, the device races and reaches up to 1232 ppm. “It doesn’t surprise me too much, it’s really one of the places where you can catch the Covid”, says a passenger on the train. “I think it’s normal since we’re all tight and it’s closed”, added another. When the windows are opened, the CO2 concentration drops immediately, to 649 ppm during this experiment.

But it is in a train, where passengers spend much more time than in the metro, that the CO2 measurement breaks records. On board a TGV, after half an hour, the sensor went from 450 to almost 1200 ppm. And it continues to increase during the journey, exceeding 2000 ppm. “We were never told of this type of control in the trains, nor of the normally acceptable limits”, laments a passenger. Hence the importance of wearing a mask in transport, which limits exposure to viral particles.

During a last stopover in a large shopping center, however, the space was large enough to prevent the air from being confined, even at the start of the sales when the crowds are increasing. The sensor is this time within the norm, its measurement climbing to around 600 ppm. Air quality is constantly monitored, as the gallery has its own devices.