[A study of the intervention effect of nose pads and elastic adjustment clasps on the fit of KN95 masks].

Objective: To investigate the fit of dust-exposed workers wearing KN95 masks in a city of Guangdong Province, and to discuss the intervention effect of nose pads and elastic adjustment clasps on the fit of KN95 masks. Methods: In January 2024, 145 dust-exposed workers from a stone processing enterprise in a city of Guangdong Province were selected as study subjects by convenience sampling, and 4 types of KN95 masks commonly used by dust-exposed workers were selected as test masks. The head and face dimensions of the study subjects were measured using a right-angle gauge and a curved-angle gauge, and the fit factor (FF) of the KN95 masks was tested using the quantitative fit test for respiratory protective equipment, and the intervention of adding nose pads or elastic adjustment clasps was given to those who failed the first fit test. The paired t-test was used to compare the changes of workers' FF before and after the intervention. Results: The coverage rate of the study population in the facial subsection of the Chinese Han population was 71.0% (103/145). Before intervention, the overall passing rate of the fit test of 4 types of KN95 masks was 16.6% (24/145), and the passing rate of 4 types of masks had statistical significance (χ(2)=19.73, P<0.001). After intervention, the overall passing rate of the fit test of masks was 33.9% (41/121), and the geometric mean of the total FF after intervention increased from 15.9 to 62.7 (t=-13.53, P<0.001), among which 88.4% (107/121) workers' FF improved after intervention, and 11.6% (14/121) of workers had reduced FF. Conclusion: Dust-exposed workers in a city of Guangdong Province have a low coverage rate of facial subsection among Chinese Han population, and the passing rate of KN95 mask fit test is low. Interventions using additional nose pads or elastic adjustment clasps can partially improve the fit of the mask, and it is still necessary to continue to explore interventions to improve the fit of mask wearers.