• The study conducted by the Respire association was carried out in two classes of a nursery school in the 9th arrondissement.

  • For Tony Renucci, acting director of Respire, "this study confirms that air purifiers are useful devices and complementary to measures to fight against air pollution".

  • Regarding the spread of Covid-19, researchers are cautious about the effectiveness of air purifiers.

To fight against particle pollution that creeps into classrooms and public buildings, should air purifiers be installed? This is what a study by the Respire association confirms, in partnership with the mayor of the 9th arrondissement, Delphine Bürkli and in conjunction with manufacturers. According to this study conducted by Olivier Blond, former director of Respire now a candidate for regional in Ile-de-France on Valérie Pécresse's list, purifiers can reduce particle pollution by 20 to 30%.

For this work, two kindergarten classes in the 9th arrondissement were equipped with purifiers and air sensors.

The air quality was measured during two weeks of testing.

The first week class A did not have an air purifier and class B had an air purifier turned on.

The second week, class A had an air purifier turned on and class B did not have an air purifier.

A difference in particle concentration was found in the order of 18.6% the first week, and 29.5% the second week in the classroom that had a purifier on.

Effective against Covid-19?

For Tony Renucci, acting director of the association Respire, “this study confirms that air purifiers are useful devices and complementary to measures to fight against air pollution”. CO2 sensors were also installed which indicated by a small indicator passing to orange then to red the concentration of CO2, signaling to the teacher that the room must be ventilated. Together, these devices "probably make it possible to fight the spread of Covid-19 in schools," says Respire, citing an Inserm study which showed that purifiers could remove 99.9% of viruses.

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, Manuel Rosa Calatrava, research director at Inserm who coordinated the study cited, is cautious: “I do not know the technical specificities of the purifiers of this company. Their markers are physical particles that have a size of 2.5 micrometers. It is a benchmark parameter in the field of indoor air quality, but does not bode well for performance against respiratory viruses, which are around 0.2 microns in size. It is a good thing to have evaluated a scrubber

in situ

, but in no case can we say that this scrubber will be effective on infectious viral particles without it being tested experimentally with the SARS-CoV-2 virus. "

In November, the National Research and Security Institute (INRS) also warned against certain so-called “anti-Covid-19” devices and specified that only devices equipped with HEPA filters of minimum class H13 “allow to effectively stop aerosols likely to carry the virus ”.

This is the case with the Natéosanté machines tested in the study, according to Olivier Blond.

Not a "magic" solution

In addition, air purifiers can in no way replace other more effective measures, reminds Gaëlle Guyot, expert researcher on ventilation issues at Cerema (Center for Studies and Expertise on Risks, environment, mobility and planning): "Scientists agree on this, the first measures to be implemented are to renew the air in buildings, whether by ventilation devices or by opening the windows. Next, we must reduce the sources of emissions into the air: reduce the number of people in the rooms, limit emissions from construction materials and cleaning products, and reduce outdoor pollution. Once these measures have been put in place, if this is insufficient, purifiers can be a complement ”,warns the researcher.

An observation to which Tony Renucci subscribes: “Air purifiers must be seen as a complement.

It is not because we put purifiers that we must continue to build schools near the roads.

This should not become an excuse to say "there is a purifier, everything is settled", it should not replace pedestrianization measures.


An experiment in Saint-Ouen, the reluctant city of Paris

Respire now wants to "extend the device to other schools and classrooms" and announces an experiment in Saint-Ouen.

The town hall of Paris, for its part, will not follow suit.

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, the public and environmental health assistant Anne Souyris specifies that the community has "made the choice of air sensors, or CO2 sensors" and that "air purifiers are not scientifically validated" , except, therefore, the one examined by the Inserm laboratory in Lyon.

Our dossier on air pollution

The deputy also fears that these devices push "not to open the windows", when we know that opening the windows helps fight against the coronavirus.

"We must be wary of magical acts, everyone wants to get rid of pollution but for the moment this has not been proven," said the elected.

And to put forward its own study, carried out at this very moment with Airparif, CNRS and Centrale supelec, which must evaluate the CO2 sensors and whose results are expected in June.


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