Facial dimensions and predictors of fit for half-mask respirators in Koreans

This study investigated the relationship between facial dimensions and the fit of half-mask respirators using fit factors and selected good facial dimension predictor(s) of fit for designing respirators for Korean workers. Three different brands of half-mask respirators-YS, SG, and 3M-were fit-tested on 112 men and 38 women using TSI Portacount 8020, and fit factors were determined. Before fit-testing, 10 facial dimensions were measured. Data were analyzed by descriptive statistics, Pearson's correlation analysis, and quadratic polynomial regression analysis with log-transformed fit factors (LNFF). However, some of the relationships between LNFF and facial dimensions in brand/gender subgroups were found to be curvilinear rather than linear. Because this result indicated that a multiple polynomial regression model including quadratic terms might be more appropriate than a multiple linear regression, data were also analyzed with a quadratic term by examination of the coefficient of partial correlation. No common facial dimension variables were found to be significant for all nine brand/gender subgroups, but the coefficient of regression for the linear term of the bitragion-menton arc was significant in five of nine brand/gender subgroups including male subjects of all three respirator brands. The 3M mask had the highest coefficient of determination values compared with other brands. Using the quadratic term for the 3M mask, face width (bizygomatic breadth) and nose protrusion were good predictors of half-mask fit. In four of nine brand/gender subgroups, nose protrusion was a good predictor of fit through analysis using a quadratic term. Results indicate that face width, bitragion-menton arc, and nose protrusion should be preferentially considered when designing a half-mask respirator for Korean workers.