Performance characteristics of the face masks
inspiratory airflow, CM
LEAKAGE
Using the “Sheffield head” system according to EN 149, in- and expiratory breathing resistance of SM and CM was similar and lower compared to FFP2, probably due to the better filter efficiency of FFP2 (Table S1). For all types of masks breathing resistance increased with higher inspiratory airflow and decreased for SM and CM under an expiratory airflow from 160 L/min due to a high leakage of the masks. The breathing resistance of FFP2 increased further, since the leakage was low. The filter efficiency was highest for FFP2 and much lower for CM and SM as expected.