It is not easy for mr. and mrs. All-the-World to make a mask craft powerful to counter the COVID-19, reveals a quebec study carried out in the last few months.
Not less than fifty or materials are passed on to the test bench of the Institut de recherche Robert-Sauvé since mid-march in order to find the best possible combinations for cover-faces effective.
Scientists have measured their ability to retain the sprays of droplets in a sneeze or a cough, for example, and to filter micro-particles emitted during breathing.
“It is very difficult to make good masks from fabrics that you would find at home,” informs the specialist in the science of aerosol and filtration Loïc Wingert, who has developed this test bench.
The Institute offers actually a few combinations that were deemed effective, but they involve materials that are more specialized that are not within the reach of all.
In other words, it is necessary to forget the cotton, felt and coffee filters to prevent the COVID-19 to clear a passage, according to this study.
Cotton can, however, serve as an envelope for the mask, for a question of comfort or appearance.
“Yes, there are a lot of masks floating around, that do not conform to our criteria, and which, to our eyes, should not be used,” said Mr. Wingert.
A good news is that the polar allows you to retain the particles that are sprayed, but its filtering capability is limited to the level of aerosols rejected by the breathing.
One of the stars of the study ? Bags vacuums, that are effective both for the spray that the filtration. However, the risk to wear such a filter close to the face is not evaluated and the company Shop-Vac, which produces it, has previously issued warnings.
“In no circumstance, someone should try to make a mask or materials of a mask from any filter manufactured, sold or distributed in the market by the Corporation Shop-Vac. These materials have not been drawn, designed or thought of for this type of use, ” he wrote on the web site.
These results did not alter the opinion of the epidemiologist Nima Machouf, who always claims that the mask should be mandatory to the inside, when the detachment physics can not be respected.
She recalled that this study has been made from a single layer of each material, and points out that the findings also support the importance of having a few layers of different fabrics for a better result.
“It is sure that this is not a mask that you will wear in the operating room or in the presence of patients of COVID. We speak in the community, she says. If we want to succeed our déconfinement, the mask is a very important tool. “
Examples of materials
For spraying and filtration
- Bags vacuums *
- For spraying : Polar
- For filtration : paper Towels, blue type Scott Shop Towels – very durable *
Not really helpful
- Coffee filters
- Microfibre cloths (for comfort only)
- Cotton (for comfort only)
*ATTENTION ! The study does not take into account the risk of wearing some of the products close to the face. It is necessary to check with the manufacturer before using a material as a filter. The complete list is available on the website of the Institut de recherche Robert-Sauvé.