Impact of structural features on dynamic breathing resistance of healthcare face mask.

In order to provide an overall evaluation and characterization of the comfort sensation and performance of face mask related to breathing resistance for healthcare in fog and haze weather, and address the influence of structural features on breathing resistance properties, an experimental set-up was developed, which was able to continuously change the direction and rate of air flow and the breathing frequency to simulate the dynamic breathing process during the actual wearing of face mask. The dynamic changes of airflow rate and the breathing resistance were acquired by a virtual instrument (VI) system and a microelectronics system. Six evaluation indices were defined for the dynamic performance and comfort sensation of face mask, derived from the source data of dynamic breathing resistance. Twelve types of face masks from different department stores with different features such as shape, respiratory valve, brand, main materials and protection level were tested using the experimental set-up. The one-way ANOVA analysis was carried out to identify the significance of the differences of the indices among the test masks. The results showed that each evaluation index was significantly different (P < 0.05) among different test masks. The change rate of breathing resistance could be obtained using the dynamic measurement of breathing resistance and could be applied for the dynamic performance evaluation of face mask compared with the static measurement of breathing resistance under constant airflow rate. The influences of structural features such as respiratory valve, shape and main materials on breathing resistance were evaluated and analyzed. The face masks with respiratory valve had lower change rate of breathing resistance. Moreover, the cup type mask had lower change rate of breathing resistance than the folding mask. Furthermore, the cotton mask had lower change rate of breathing resistance than the nonwoven fabric mask.