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Figure 2. Facial measurement using a 3D scanning device; This figure shows the process of measuring a facial model using a 3D measuring device; The facial model with the mask was measured from various angles to obtain the coordinate data.

Figure 3. Facial model viewed from various angles (small face); This figure illustrates the observation and measurement of computer graphics created based on the coordinate data measured using a 3D measuring device from various angles.

Figure 4. Procedure for measuring air leakage rate; <b>A</b> shows the setup for measuring air leakage rate from a mask during simulated exhalation using a facial model in a laboratory setting. The mask-fitting tester MT-05U was used for the measurements. A particle generator maintained a constant particle concentration in the room, and exhaled air was simulated using a nebulizer. <b>B</b> is a photograph illustrating the exhalation process, in which simulated exhaled air is released through tubes positioned within the nasal and oral cavities of the facial model.

Figure 5. Graph showing air leakage rates in relation to facial shape and mask size (two-way ANOVA); There was an interaction between facial shape and mask size

Figure 6. Graph comparing air leakage rates based on face shape and mask size (one-way ANOVA); The air leakage rate for the small face with an S-sized mask was higher than that for the medium and large faces with either mask.