The researchers found that wearing a mask while talking reduced particles directly through the mask by an average of 93%, from the bottom by 91%, the sides by 85% and the top by 47%, although with substantial variability between individuals. They got similar results for coughing.
“While air escape does limit the overall efficiency of surgical masks at reducing expiratory particle emissions, such masks nonetheless provide substantial reduction,” Cappa said. “Our results confirm that mask-wearing provides a significant reduction in the probability of disease transmission via expiratory particles, especially when both infected and susceptible individuals wear masks.”