A new study examines the efficacy of particle filtration by woven fabric, which consists of fibers twisted together into yarns. There are, therefore, two lengthscales: the diameters of the fiber and the yarn. Using 3D imagery produced by confocal microscopy to see the air flow channels, the scientists simulate the airflow through these channels and calculate filtration efficiency for particles a micrometer and larger in diameter. The study concludes for particles in this size range, the filtration efficiency is low.