Is a surgical mask necessarily for single use?

The recommendation of the health authorities is clear: the surgical mask must be thrown after use.But faced with the waste that accumulates and the cost borne by citizens, votes plead for their reuse subject, for the general public.

"Medical masks are for single use.Throw the mask immediately, "said the World Health Organization (WHO).

Despite everything, in the event of a shortage like that of the beginning of the COVVI-19 pandemic, the WHO admits exceptional procedures for decontamination of masks to allow their reuse.

The American Agency for Medicines (FDA) has also emergency a process of decontamination of N95 masks (for caregivers, equivalent to FFP2) by spraying hydrogen peroxide.

Other methods exist in a professional context such as exposure to high temperatures or irradiation to ultraviolet.

"But it is not practical for individuals," notes Denis Corpet, microbiologist and hygiene teacher, member of Adios Corona, collective of French scientists from various specialties.

So to limit plastic pollution generated by these polypropylene masks and family expenses, Adios Corona pleads - in a domestic context where people are not exposed to viral charges comparable to caregivers of resuscitation - for the "method of envelopes»».

Place your used mask (unless it is damaged) in a paper envelope, by registering the date, and leave it there for seven days.

"Several scientific studies show that on a mask, viruses (from Sars-Cov-2) are almost all dead in 7 days", justifies Denis Corpet.

Thus, according to the results of a team from the University of Hong Kong published in The Lancet, only 0.1 % of the volume of virus is still detectable on the outside of the mask after a week.

Peter Tsai, inventor of the electrostatic load technology of N95 masks, which makes it possible to attract particles to prevent them from passing, also subscribes to the seven -day method.

"To limit consumption and preserve the environment, I would recommend reusing the mask after seven days, 5 to 10 times for the general population.As I do, "he said to AFP.

It also evokes the possibility of passing the mask in the oven - not too hot to prevent plastic from burning, but enough to kill the virus."The temperature must be controlled to stay between 70 and 75 ° C," insists the retired scientist who resumed service at the University of Tennessee during this COVVI-19 crisis.

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"Like underwear"

On the other hand, he advises against washing masks: "Washing without laundry may not make the virus disappear.Washing with detergent will destroy the load (electrostatic), ”he says.However, he believes that despite this wide drop in filtration capacity, a machine -past mask could be more effective than a fabric mask.

This is the conclusion of tests carried out by the French Defense of Consumer Defense Group UFC-Que Choisir, published this week.

Three masks with filtration standards of 95 % particles of 3 microns were switched to the machine at 60 ° C, then to the dryer and ironed.

Result, after 10 similar treatments, the three models keep filtration capacities at least 90 %."Despite a slight felting, the washed surgical masks are therefore equal, and beyond, with the most efficient fabric masks," says the UFC-Que Choisir this week.

Results similar to those obtained by Philippe Vroman, researcher at the Gemtex laboratory of the Textile Engineering School in Roubaix, who has tested three models so far.

After at least five washes, "there is practically no difference (filtration) for the particles of 3 microns, the difference is made for smaller particles", assures the scientist, which is based on preliminary results notstill published.

These masks "therefore remain perfectly positioned to play their general public role", he estimates, referring to the standards applied in France for fabric masks, the highest of which requires a filtration of 90 % of the particles of 3 microns.

"And I prefer that we change masks every 4 hours and can be washed, rather than wearing them several days in a row like some.It's a bit like underwear...", He continues.

But without scientific publication, the recommendations of the health authorities do not change.

"Single -use surgical masks must be thrown into a trash can after use," insisted this week the General Directorate of French Health, noting, however, that "work is underway in France" on the question of the reuse of masks.

"I don't think (a surgical mask) is washable," also challenges Kaiming Ye, director of the Biomedical Engineering Department at the American University of Binghamton.

It is possibly possible to "reuse" a medical mask, "but in -depth tests must be carried out", insists with the AFP the researcher who works on standards of decontamination by ultraviolet -associated radiation associated with ozone.