Study Reveals Most Effective Face Masks for Reducing COVID-19 Transmission

Researchers at the American University of Duke had several masked participants speak in a dark room towards a laser beam. They were asked to repeat: "Stay healthy, people", "take care of yourself". The number of droplets and droplets crossing the beam was analyzed by computer and the results are clear. "Masks reserved for hospital staff are the most effective". They reduce "the transmission of droplets by more than 99.9%, compared to a person speaking without a mask". Then come the three-layer medical masks, reliable at over 90%, and just behind the polypropylene and cotton/polypropylene masks.

As for homemade cotton masks, "the reduction oscillates between 70 and 90%, depending on the number of layers and the pleating". Bandanas reduce droplets by 50%. As for the fleece neck warmer, it is at the bottom of the ranking. It is the type "that runners use".

Professional N95 medical masks equipped with a round valve are much worse than N95s without a valve. They are sold as "breathable", but the authorities and experts advise against them because "they more easily spread the air exhaled by an infected person," the same source said.