A new study highlights the need for widespread use of better face masks and the importance of good ventilation to mitigate the spread of COVID-19 indoors. Engineering researchers at the University of Waterloo performed experiments using a mannequin to simulate a seated person breathing in a large room. The studies showed a significant buildup over time of aerosol droplets exhaled droplets so tiny they remain suspended and travel through the air despite the use of common cloth and blue surgical masks. By contrast, higher-quality, more expensive N95 and KN95 masks filtered more than 50 per cent of the exhaled aerosols that can accumulate indoors and spread the COVID-19 virus when inhaled by other people. Yarusevych, the principal investigator in the Fluid Mechanics Research Lab, said the much greater effectiveness of N95 and KN95 masks versus cloth and surgical masks makes a compelling case they should be worn in indoor settings, such as schools and workplaces, as much as possible.