Testing of outward leakage of different types of masks with a breathing manikin head, ultraviolet light and coloured water mist

Since the outbreak of COVID-19, wearing a mask, voluntary or obligatory, has led to diverse and numerous designs. Guidelines for minimum requirements include tests for visual inspection, strength, filtration, and breathing resistance, but not for the fit of a mask. The fit of a mask was assessed by testing the outward leakage of exhaled breath based on the visualization of coloured mist exhaled by a manikin head. Fourteen masks were selected based on differences in design, such as type of material, shape (cheek wings vs. none), filter type, and the number of layers. Leakage expressed in mean mist percentages (visualized with a camera), patterns of coloured mist left inside the masks, as well as visual fit of the masks on the manikin head, showed that a loose fit mask results in more leakage. Also, combining quantitative with qualitative assessment proved to be complementary. Future tests should be conducted on a range of users, covering the best fit over time as well breathability, use, and comfort. The use of face masks, whatever their characteristics, seem an adequate strategy to reduce the dispersion of potential ‘infected’ aerosols into the space from people, as opposed to not wearing one.