Although the industry has recovered from the shock of the early days of the COVID-19 pandemic and is now producing enough face masks of various types, most people in the world use homemade options for various reasons. Everyone understands that they are less effective than professional medical models, but the question is: how much? Duke University (USA) has developed an easy way to test masks and tested the most popular samples.
The test device consists of a dark chamber into which a laser beam is fed through a lens. It dissipates and covers a wide area inside the chamber, illuminating all particles that fly in the air. The masked man brings his face to the camera and says a few phrases, exhaling air inward. The camera captures laser flashes when liquid droplets in the exhalation intersect with the beam.
The first conclusion: drops of liquid are actively released even during normal conversation in a mask. A person does not need to cough or sneeze - he can spread the infection through the mask, believing that the protection is working. But the real surprise for the researchers was the fact that N95 valve medical masks release far more particles than a rag mask. The reason is that the valve closes on inhalation, but opens on exhalation, so the wearer of the mask is protected from infection, but he himself can be a distributor of the virus.
The most strange and sad thing was shown by checking masks made of fleece and similar common materials. The structure of this tissue breaks down large droplets of saliva into small ones, which much more easily pass through barriers and are carried through the air. This is precisely the paradoxical case when it is better not to wear a mask at all than to use a fleece product, although everyday logic seems to say the opposite.