Fig 1.
(a) Disposable procedure mask: Henan Liwei Biological Pharmaceutical Co. Ltd; (b) Multi-layer mask: four layered system comprised of two layers of quilt batting between an outer and inner layer of cotton; (c) Non-woven polypropylene ‘craft’ material (manufactured by smart-fab®); (d) “N95-like” electret filter membrane material (purchased from Amazon.ca) used as the middle filter layer, as part of a multi-layer mask; (e) 2-Layer mask: quilt batting/cotton mask; (f) KN95 mask: MedSup Canada Protective Face Mask, and; (g) N95 FFR: 3M™ model 9210.
Fig 2.
Schematic of aerosol swatch penetration set-up.
A polydisperse NaCl aerosol is generated in the mixing chamber and pulled through the charge neutralizer and swatch test rig using a regenerative blower. Air flow is regulated using the flow meter. Aerosol concentration, upstream and downstream, is measured with the SMPS/APS as shown.
Fig 3.
Total inward leakage test being performed on the 3M™ model 9210 N95 FFR.
The Sampling probe for the TSI Portacount 8038 is shown to be connected to the respirator by use of a sampling probe supplied by TSI. The operator is shown to be wearing a loose-fitted PAPR and nitrile gloves as a health and safety precaution from working in close proximity to the test volunteers during the COVID-19 pandemic.
Fig 4.
Mean penetration profile as a function of aerodynamic particle diameter for the material of five fabric masks comprised of 2 layers.
Note, the penetration range is 0 to 100%. Materials included quilt batting, cotton, nylon, polyester and silk.
Table 1.
Maximum penetration, geometric mean FPF, percent overall penetration, inhalation pressure drop and face velocity for the five mask groups: Fabric 2-layer, multi-layer, disposable procedure, KN95 and N95 FFRs.
Fig 5.
Mean penetration profile as a function of aerodynamic particle diameter for the material of seven fabric masks with an internal layer to augment filtration.
Note, the penetration range is 0 to 100%. Multi-layer material systems included: i) cotton/electret furnace filter/cotton, ii) cotton/procedure mask/cotton, iii) cotton/electret filter membrane/cotton, iv) cotton/quilt batting/cotton, v) cotton/polypropylene shopping bag/cotton, vi) cotton/polypropylene craft 1/cotton, and vii) cotton/polypropylene craft 2/cotton.
Fig 6.
Mean penetration profile as a function of aerodynamic particle diameter for the filter material of six disposable procedure masks.
Note, the penetration range is 0 to 100%. The bump in the penetration data between the particle range 0.5 to 0.67 μm is related to averaging the SMPS and APS measurements.
Fig 7.
Mean penetration profile as a function of aerodynamic particle diameter for the filter material of two KN95 masks (five replicates each).
Note, the penetration range is 0 to 20%.
Fig 8.
Mean penetration profile as a function of aerodynamic particle diameter for the filter material of five N95 FFRs (three replicates each).
Note, the penetration range is 0 to 20%.
Fig 9.
Protection performance results for the five mask groups; fabric 2-layer masks (2-L), multi-layer masks (M-L), disposable procedure masks (PMs), KN95 masks and N95 FFRs.
TILPF—total inward leakage protection factor. FPF—fabric protection factor (overall protection of fabric material against entire particle size distribution). FF—fit factor (total inward leakage measured through face seal only (by QNFT). Sample sizes: n = 8 to 26 for TILPF; n = 6 to 20 for FPF; and; n = 30 for FF. The geometric mean is shown by the square marker.
Table 2.
Percent reduction in penetrated virion for each mask group compared to the fabric 2-layer mask: Results for 0.3 μm particle diameter at a viral concentration of 0.01%, and results for the particle diameter associated with the maximum virion penetration at 1.0% concentration.
Fig 10.
QF values for the fabric 2-layer, multi-layer, disposable procedure/surgical and KN95 mask groups.
As the face velocities used in filtration testing for the N95 FFR group were dissimilar to the other three mask groups, their QF values were not plotted for comparison in this figure. DPM = disposable procedure mask.