https://www.sciencedaily.com/releases/2021/10/211005124725.htm

"Mask mandates and good ventilation are critically important to curb the spread of more contagious strains of COVID-19, especially during the flu season and winter months as more people socialize indoors," says Saad Akhtar, a former doctoral student under the supervision of Professor Agus Sasmito at McGill University.

While most public health guidelines recommend physical distancing of two metres for people from different households, the researchers say distancing alone is not enough to prevent the spread of COVID-19. In a study published in Building and Environment, the researchers found that when people are unmasked, more than 70 percent of airborne particles pass the two metres threshold within the 30 seconds. By contrast, less than 1 percent of particles cross the two-metre mark if masks are worn.