This week's New England Journal of Medicine has a video using Schlieren optics demonstrating the plume created by a cough with no mask, with a surgical mask and with an N95 mask.The masks redirect the plume upward which may reduce the risk of transmission of respiratory infections.Schlieren photography allows visualization of transparent material that is not visible to the human eye. The Schlieren photo of a cough shown here (with no mask) is from the New York Times (10/28/08) by Madeleine Robins.
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