Filtration efficiency of face masks and veils during COVID-19 pandemic
Wearing face masks have been implemented as a public and personal health control measure against the spread of coronavirus disease (COVID-19). However, the protection level of non-medical face masks, such as women face veils, is still uncertain. This study aimed to assess the filtration efficiency (FE) of different type of medical masks (either as sealed or unsealed, single or doubled), non-medical masks (cloth masks) and face veils. FE of face masks was evaluated using an in-house 3D-printed air duct connected to the Aerotrak particle counter with a capability of counting particle sizes of 0.3, 0.5, 0.7, 1, 2 and 5 µm. A set of 10 earloop surgical masks,10 tie-on surgical masks, 3 triple layers reusable cloth masks and 3 types (short, medium and long) of traditional face veils were included in the study. The unsealed surgical masks showed intermediate FE (36.54-80.58%), with no observed differences between tie-on and earloop or single and doubled masks. The means FE values, for each particle size, of sealed surgical masks (FE=99.16-100.00%) was significantly higher (P<0.05) than the unsealed ones. No significant difference was observed in the mean FE values between unsealed surgical masks and either cloth masks (FE=23.19-75.35%, P= 0.26) or face veils (FE=19.10-70.68%, P=0.14). However, wearing a surgical mask under the face veil significantly improve the FE (33.73-79.18%; P<0.001). We conclude that beside sealed surgical masks that ensure optimal filteration, the unsealed surgical and cloth masks and face veils showed comparable performance and acceptable protection at the 5 µm particle size which is the most relevant to COVID-19 infectious droplets.