Evaluating the filtration efficiency of commercial facemasks’ materials against respiratory aerosol droplets
Creators: name: Patra, Satya S.
name: Nath, Jyotishree
name: Panda, Subhasmita
name: Das, Trupti
name: Ramasamy, Boopathy
Publisher: name: Taylor & Francis
Year: 2021
Subjects: subject: Biochemistry
subject: Space Science
subject: Biotechnology
subject: Evolutionary Biology
subject: FOS: Biological sciences
subject: 59999 Environmental Sciences not elsewhere classified
subject: FOS: Earth and related environmental sciences
subject: 39999 Chemical Sciences not elsewhere classified
subject: FOS: Chemical sciences
subject: 69999 Biological Sciences not elsewhere classified
subject: Science Policy
subject: Hematology
subject: Computational Biology

description: Respiratory droplets serve as a viable transmission mechanism for many viruses and other pathogens. Facemasks are commonly used to minimize the risk of this transmission. However, information on the size-resolved filtration efficiency of commonly available commercial facemasks is not readily available in the literature. To fill this gap, the current study performs aerosolized chamber experiments to evaluate the filtration efficiencies of commonly available commercial facemasks’ materials in a size range of 0.3–10 µm. Results rank the performance of filtration through commercial facemasks’ materials as follows (values in brackets indicate the average filtration efficiencies across 0.3–10 µm): 6-Layer N95 mask (0.918) &gt; N95 mask – without valve (0.88) &gt; KN95 mask (0.84) &gt; N95 mask -with valve (0.834) &gt; Heavy knitted cotton mask (0.808) &gt; Surgical mask (0.778) &gt; Cotton mask-2 layers (0.744) &gt; Nylon fabric mask-2 layers (0.740) &gt; T-shirt fabric mask-2 layers (0.708) &gt; T-shirt fabric mask-1 layer (0.648). The size-resolved filtration efficiencies through the material across the evaluated commercial facemasks ranged from 38–83% in the size range of 0.3–0.5 µm, 55–88% in the size range of 0.5–1 µm, 69–93% in the size range of 1–2.5 µm, 76–96% in the size range of 2.5–5 µm, and 86–99% in the size range of 5–10 µm. Subsequently, the filtration efficiencies of materials post washing (with detergent in warm water and allowing to dry completely) were also evaluated. The average reduction in filtration efficiencies post washing are as follows: 6-Layer N95 mask: 3%, N95 mask – without valve: 2%, KN95 mask: 4%, N95 mask -with valve: 3%, Heavy knitted cotton mask: 4%, Surgical mask: 18%, Cotton mask-2 layers: 11%, Nylon fabric mask-2 layers: 6%, T-shirt fabric mask-2 layers: 6%, T-shirt fabric mask-1 layer: 8%. This decrease in the filtration efficiency was more pronounced for the sub-micron particles than the super-micron ones. <i>Implications</i>: Facemasks are commonly used to minimize the risk of pathogens through ambient air transmission. However, information on the size-resolved filtration efficiency of commonly available commercial facemasks materials is not readily available in the literature. To fill this gap, the current study performs aerosolized chamber experiments to evaluate the filtration efficiencies of commonly available commercial facemasks materials in a size range of 0.3–10 µm. The performance of the commercial facemasks materials as follows in the order of (values in brackets indicate the average filtration efficiencies across 0.3–10 µm): 6-Layer N95 mask (0.918) &gt; N95 mask – without valve (0.88) &gt; KN95 mask (0.84) &gt; N95 mask -with valve (0.834) &gt; Heavy knitted cotton mask (0.808) &gt; Surgical mask (0.778) &gt; Cotton mask-2 layers (0.744) &gt; Nylon fabric mask-2 layers (0.740) &gt; T-shirt fabric mask-2 layers (0.708) &gt; T-shirt fabric mask-1 layer (0.648). The choice of facemask is greatly driven by the size of viable respiratory droplets that need to be eliminated. If droplets with particle size less than 0.5 µm are required to be filtered, N95 masks without the valve or more layers are preferred. If the primary objective is to filter particles between 0.5–1 µm, then N95 (both with or without valves) or KN95 masks are recommended. Surgical masks and heavy knitted cotton masks may also be used for this purpose, but with caution.