This document specifies the testing instruments and procedure for determining the filtration efficiencies of flat sheet filter media against airborne nanoparticles in the range of 3 nm to 30 nm. The testing methods in this document are limited to spherical or nearly-spherical particles to avoid uncertainties due to the particle shape.st edition 2019-03 Test method to measure the efficiency of air filtration media against spherical nanomaterials — Part 2: Size range from 3 nm to 30 nm Méthode d'essai pour mesurer l'efficacité des médias de filtration d'air par rapport aux nanomatériaux sphériques — Partie 2: Spectre granulométrique de 3 nm à 30 nm Reference number ISO/TS 21083-2:2019(E) ？ ISO 2019 ISO/TS 21083-2:2019(