Scenes of office life, almost two years after the start of the Covid-19 pandemic. The coffee break is back, as is the group canteen and party favors, while teleworking is rarer. Consequence: more people in business and a relaxation on the wearing of the mask (always on the nose, not below). These are all factors that favor aerosol contamination, the main cause of the resurgence of the disease, the fifth wave of which has been visible in France for nearly two weeks.
As for the ventilation of enclosed spaces, one of the barrier gestures relentlessly praised by scientists, it becomes rarer with the approach of winter. While the virus is transmitted mainly in closed and poorly ventilated spaces, according to epidemiologists, monitoring of air quality in companies acts as a blind spot in the fight against Covid-19. Advocated by the executive, it has so far never been included in the list of obligations made to companies to contain the spread of the virus.
Before the implementation of a new health protocol in companies, Monday, November 29, the current text reminds us that “control of aeration / ventilation is an essential measure for preventing situations at risk of aerosolization of Sars-CoV-2”, and adds that he “is necessary to ventilate the premises by natural or mechanical ventilation in working order.”
“To renew and clean the air, you need a minimum ventilation rate of around 25 cubic meters of fresh air, per hour and per occupant, in offices”, specifies to Franceinfo the doctor Fabien Squinazi, medical biologist and vice-president within the High Council of public health (HCSP). So much for the rules provided for a long time by the Labor Code. But how do you know if an enclosed space is well or poorly ventilated? A polluting gas, linked to human presence, betrays the lack of ventilation: carbon dioxide (CO2).
“We talk a lot about the level of CO2 at the moment because it is an indicator of human presence linked to breathing. If we see it increasing in a room, it shows a ventilation problem.”
Fabien Squinazi, medical biologistto franceinfo
Hence the success of CO2 sensors (or detectors), these small devices which made a lot of talk about them when they were installed in schools at the start of the 2021 school year. This equipment financed by the municipalities, with promised aid from the State, is indeed recommended – but not made compulsory – by the health protocol of the National Education for the year 2021-2022.
In establishments open to the public (ERP), and in particular schools, it was necessary, before the Covid-19 epidemic, “ensure that the CO2 concentration level does not exceed a maximum pollution threshold of 1000 ppm [pour partie par million, soit le nombre de molécules de polluants sur un million de molécules d’air]“, explains Fabien Squinazi. “During the Covid period, the High Council for Public Health recommended lowering this threshold to 800 ppm”. Because the higher the concentration of CO2, the greater the risk of the virus circulating in the confined air of a closed room.
But companies, they are still far from having adopted these small boxes, the use of which is however recommended by the Scientific Council Covid-19, in its opinion dated November 20, 2021. The government did not want to impose them , probably because of their cost (between 100 and 300 euros for standard models). And on the side of the unions, the introduction of CO2 sensors is not really in the range of priority demands. “No, we are not asking for it at the moment”, replied, surprised, the Deputy Secretary General in charge of quality at work at Unsa, Dominique Corona. “But indeed, it might be time to put back some ventilation and [contrôle de la] air quality”.
By citing a long-term study by the Institut Pasteur on the “behaviors and practices associated with infection” by the virus, the Ministry of Labor recognized, however, in March 2021, that the workplace could be a major source of contamination.
“The professional environment (…) represents 15% of contaminations when the source is known.”
The Ministry of Laborin an update of the corporate health protocol dated March 23, 2021
A new study by the Pasteur Institute on the spread of the Delta variant in France this summer, published Friday, November 26 in the medical journal The Lancet Regional Health Europe (in English), does not show an increased risk linked to work. But she confirms that the increased risk in poorly ventilated areas comes from the fact that Sars-CoV-2 is transmitted massively through aerosols, those clouds of particles that we emit when we breathe, and even more when we talk, shout or shout. let’s sing.
While these CO2 sensors can reassure employees about their working conditions, they can also function as a double trigger warning: remember to wear the mask, on the one hand, and ventilate, or leave a crowded room if it is. is poorly ventilated, on the other hand. “These devices are a warning signal that any employee can see”, exposes Fabien Squinazi. “There are sensors to be located at the height of the respiratory tract which are effective and allow the CO2 level to be measured reliably., he continues. But, for the moment, it is rather the communities, the schools which equip themselves “, notes Julien Martin, sales engineer for the company Quos, which specializes in measuring and improving air quality. He nevertheless noted the start of a wider awareness within companies.
“During the second lockdown, there was a thrill over the demand for air sensors at large companies and among office property developers.”
Julien Martin, engineer in a company specializing in air quality measurementto franceinfo
A large company, whose name he does not wish to reveal, has asked him “air monitoring and purification tools” before moving to new premises, where meetings will be held in “Glass bubbles located inside an open space, which are outside the overall ventilation system. But for the moment, these are companies that have the means to invest”.
“On CO2 sensors, the market is still in its infancy”, outbid Jean-François Merle, vice-president of the group of experts entitled “Filtration and purification for air quality” within the union of thermal and aeraulic industries (the science which studies the flow of uncompressed air in ducts) and Uniclima refrigerators. Before noting that “Asian countries like Japan have a much better air quality culture than ours. We are only just starting to talk about it. As long as there is no strict legislation requiring a sensor. of CO2 in the premises, such equipment will remain rare, even if it is moving in the industry “. Regarding sales, he says he has no figure or estimate to give for the moment.