What is the must-have item in 2020? I believe face mask is the obvious answer. Face mask becomes world popular because it is the only available tool which human beings can use to protect from the pandemic COVID-19.
In February, when the COVID-19 was spreading over China, face mask no matter cloth mask or surgical mask had all been sold out. At that time, people cannot find even one mask anywhere. Therefore, we have to make our own face masks by tailoring old clothes.
How is the filter performance of cloth mask and surgical mask?
Inexpensive cloth masks are widely used in developing countries to protect from particulate pollution albeit limited data on their efficacy exists. Surgical masks have been used since the early 1900s to minimize infection of surgical wounds from wearer-generated bacteria. The goal of this study was to evaluate the filter performance and facial fit of samples of surgical masks and cloth masks.
We examined the efficiency of four types of masks (three types of cloth masks and one type of surgical mask) commonly worn in the developing world. Five monodispersed polystyrene latex microsphere size (30nm, 100nm, and 500 nm, and 1 and 2.5 μm) and diluted whole diesel exhaust was used to assess facemask performance. Among the three cloth mask types, a cloth mask with an exhaust valve performed best with filtration efficiency of 80-90% for the measured polystyrene latex (PSL) particle sizes. Two styles of commercially available fabric masks were the least effective with a filtration efficiency of 39-65% for polystyrene latex beads, and they performed better as the particle size increased. When the cloth masks were tested against lab-generated whole diesel particles, the filtration efficiency for three particle sizes (30, 100, and 500 nm) ranged from 15% to 57%. Standard N95 mask performance was used as a control to compare the results with cloth masks, and our results suggest that cloth masks are only marginally beneficial in protecting individuals from particles<2.5 μm. Compared with cloth masks, disposable surgical masks are more effective in reducing particulate exposure.
There is ongoing debate, however, whether surgical masks can meet the expectations of respiratory protection devices. We carried out another experiment to evaluate the filter performance and facial fit of a sample of surgical masks.
Filter penetration was measured for at least 3 replicates of 9 surgical masks using monodisperse PS latex sphere aerosols (0.895, 2.0, and 3.1 μm) at 6 L/min and 0.075-μm sodium chloride particles at 84 L/min. Facial fit was measured on 20 subjects for the 5 masks with lowest particle penetration, using both qualitative and quantitative fit tests.
Masks typically used in dental settings collected particles with significantly lower efficiency than those typically used in hospital settings. All subjects failed the unassisted qualitative fit test on the first exercise (normal breathing). Eighteen subjects failed the assisted qualitative fit tests; 60% failed on the first exercise. Quantitative fit factors ranged from 2.5 to 9.6.
None of these surgical masks exhibited adequate filter performance and facial fit characteristics to be considered as respiratory protection devices, which also explains why so many medical personnel get infected when exposed into high concentration of COVID-19 virus.