SNCF air filtration standards “are not suitable”, according to a researcher

SNCF air filtration standards “are not suitable”, according to a researcher
SNCF air filtration standards “are not suitable”, according to a researcher

“SNCF standards are not adapted to Covid, but rather to normal working conditions”, alert Saturday June 5 on franceinfo the researcher at the École normale supérieure (ENS), Bruno Andreotti. A report from the Rhône labor inspectorate, unveiled by Mediapart [article payant], reports an excessively high level of CO2 in the trains and insufficient air renewal. The physics professor at the University of Paris says that sometimes “air intakes are closed” or that “the probes no longer work”.

franceinfo: Does this report from the labor inspectorate worry you?

Bruno Andreotti: We must not create psychosis, but the rates are too high. What is considered a good standard of ventilation in spaces that welcome masked public is 800 ppm (parts per million) of CO2. SNCF replies that the threshold is raised to 5,000 ppm for rail. Except that the SNCF standards are not adapted to the Covid, but rather to normal working conditions. However, efforts are needed in all public spaces to continue to have the epidemic descent that we have known for five weeks. Many travelers equipped with CO2 sensors report their measurements on social networks. From time to time, we meet SNCF standards, which are already too high, and from time to time, we notice that the air intakes are closed or that the probes no longer work. This leads to excess CO2. Another thing pointed out by the report is that there are outright wagons, TGV trailers in which the ventilation is deactivated after passing through a tunnel or under special circumstances.

Unlike airplanes, TGVs are not equipped with high performance filters. How is this a problem?

In all spaces of this type, there is a ventilation part, i.e. replacement of stale air with fresh air, and an air conditioning part, i.e. in which the stale air is taken back and it is retreated in temperature, humidity and filtration to return it. In trains, it is in the air that comes along the windows.

“We only have a third of fresh air and two thirds that recycle the cabin. If we don’t remove the viral particles before sending them back through the windows, it makes things worse because we increase the circulation of viral particles. “

Bruno Andreotti, researcher at ENS

to franceinfo

So, you absolutely need the right level of filter quality, that is, holes small enough to stop virus particles that are a fraction of a micron. It is much smaller than a hair. For the moment in France, these are rather coarse filters which stop the coarse dust. We can protect ourselves from this by putting on quality masks and FFP2 well glued to the face, surgical masks plated by a mask.

Does the mask guarantee to protect us against contamination, even for trips of several hours sitting next to another passenger?

It never guarantees. We cannot avoid that there may be small leaks along the mask. But by paying a little attention, we go down to very low levels of risk. It assumes either that the dining cars do not reopen on June 9, or that there is a particular effort to purify the air in these cars. For example, in Italy, in recent weeks, there has been an investment of 50 million euros to equip all Italian TGVs with filters that give acceptable air quality standards.

 
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