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Effect of air ion emission on the penetration efficiency of two respiratory masks: N95 respirator (a) and surgical mask (b). The penetration efficiency measured with no ion emission (circles) is compared to that obtained with the negative ion emission (Ni∼1.3×106 e− cm−3) during t=3 min (void circles); t=6 min (squares); t=9 min (void squares); and t=12 min (triangles).
