Fig 1.
Ultra fit mask for reducing face seal leakage on the periphery of the mask body.
(A) Ultra Fit Mask (UFM) fitted on a head form compliant to ISO 16976–2 Respiratory Protective Devices (medium size). (B) Exterior and interior schematics of prototype UFM. (C) Additional cough-trapping inner flap layer attached on the interior side is highlighted in blue.
Fig 2.
Evaluation of exhaled vapor using laser scattering.
(A, C) Side-view and front-view exhaled vapor imaging and histograms of the segmented area (white dotted box). Red arrows indicate particles that escaped the mask, while yellow arrows indicate particles that passed through the mask filter material. (B, D) Normalized laser scattering of the segmented forehead and lateral regions over an exhalation period.
Fig 3.
Infrared thermal imaging of mask surface over breathing cycles.
(A) Infrared thermal snapshots at the end of inhalation and exhalation with 3-ply mask (3PM) and UFM were obtained from video recordings of breathing cycles. Three subregions at the left and right side of the nose (red dotted boxes, 5 x 5 pixels), and the center of the mask (red dotted box, 20 x 20 pixels) were selected for thermal variation analysis over multiple respiration cycles. Thermal variation of the (B) center subregion and the (C) left and right side of the nose over a 120-second breathing cycle.
Fig 4.
Aerosol dye examination of 3PM and UFM.
(A) Schematic of the experimental setup where an aerosolized fluorescent dye was nebulized in the vicinity of the headform, with exhalation and inhalation breathing simulated by a modified resuscitator. (B) Fluorescent droplets deposited on a NIOSH medium headform with no mask, 3PM, and UFM. For scale, each image measures ca. 18 cm wide. A lower percentage of dye coverage indicates improved protection from external aerosol droplets. (C) Relative exposure of the mannequin to aerosols assessed by the relative area covered by aerosolized fluorescent dye. Results represent the mean ± SD of 6 repeated trials. * and **** indicate adjusted P < 0.05 and P < 0.0001 compared via a one-way ANOVA with Tukey post-hoc test.
Fig 5.
Quantitative fit test results of 3PM, KF94 and UFM.
(A) Overall fit factors of quantitative fit test by PortaCount® 8038 for n = 13 volunteers with 3PM, KF94 and UFM. (B) Fit factors between novice (n = 10) and experienced users (n = 3). (C) Effects of facial hair with 3PM and UFM groups. UFM with no hair outperformed both 3PM with and without hair and as well as UFM with hair. was used. (D) Exercise-specific fit factors measured with PortaCount® 8038 of 3PM, KF94 and UFM. After reading a provided rainbow passage (‘Talking’), a non-measuring grimace exercise was performed per the OSHA fit test protocol. The post-grimace normal breathing exercise was labelled as ‘Normal Breathing 2’ to differentiate from the earlier normal breathing (‘Normal Breathing 1’). Bars are of the mean with error bars indicating the standard deviation. A Friedman test was performed for statistical analysis. *, **, ***, and **** indicate adjusted p-values of less than 0.05, 0.01, 0.001, and 0.0001, respectively.
Fig 6.
Model of airborne infection risk by mask type and usage.
(A) The relative risk of a new airborne infection occurring in a classroom type environment with varying rates of masking and mask types. (B) The calculated individual infection risk parameter for individuals riding a subway train, assuming the presence of an infective individual. The dashed purple line indicates the risk parameter for no masking.