Necessary conditions of the length and correct way of wearing of a nonmedical mask for younger Japanese women

Abstract

Textile masks used in industrial, medical and daily settings cover the wearer’s nose and closed and open mouth. Masks have been made by different mask manufacturers as a result of the sudden shortage of masks due to the coronavirus disease 2019 pandemic. However, there has been no clear standard design of a mask for daily use. Therefore, this study obtained the necessary conditions of the shape and length of the mask sheet and the correct way of wearing for 99.7% of a target population. The examination was based on newly acquired data for Japanese young women (20–27 years of age) under an open-mouth condition. In the anthropometry, the three-dimensional facial shape was measured for 68 women through three-dimensional motion capture. Using the three-dimensional coordinates, sheet patterns of four sizes constructed from triangles were analyzed. The third and fourth largest patterns were shown to have higher fitting performance in a t-test. Moreover, the numbers of people suited to the patterns calculated using a cumulative distribution function reveal that the third largest pattern had a proper length of the sheet that was not oversized. The necessary lengths of the sheet for 99.7% of the target population under open-mouth conditions were 130.4 mm and 148.5 mm in the horizontal and vertical direction, respectively. The present study thus provided the necessary conditions and correct way of wearing for the sheet design. The masks should be further studied in terms of their wearability, filtration and comfort in the near future.