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We aimed to compare the effectiveness of different masks in limiting the dispersion of coughed air.

We employed the single-curved mirror Schlieren method. Coughed air with a slightly higher temperature than the ambient air generates a refractive index gradient. We used a spherical mirror with a radius of curvature of 10 m and a diameter of 60 cm. The spread of the cough wavefront was investigated among five subjects wearing (1) no mask, (2) single surgical mask, (3) double surgical masks, (4) cloth mask, 5) valveless N95 mask or 6) valved N95 mask.

All mask types significantly reduced the magnitude of the dispersion of the contaminated region. The percent reduction in the cross sectional area of the contaminated region for the same mask types but different subjects revealed by the normalized data suggests that the fitting of the masks play an important role.

We observed no …