The International Organization for Standardization (ISO) has published standard ISO/TS 21237:2020, “Nanotechnologies — Air filter media containing polymeric nanofibres — Specification of characteristics and measurement methods.” According to ISO, in recent years, air filter media containing nanofibers have been commercialized and widely used by different industries due to their high filtration efficiency, along with a low pressure drop created by the slip flow effect. ISO states that different techniques, such as electrospinning and force spinning, have been used to produce air filter media containing nanofibers. Nanofibers can exhibit different crystalline structures, morphology, and diameters. Polymeric nanofibers, such as polyamide, polyvinylidene fluoride, polyacrylonitrile, and polyurethane, are typically used for air filter media. ISO notes that nanofibers can be deposited on different kinds of woven and nonwoven substrates. According to ISO, the standard is intended to facilitate communication between sellers and buyers and to support the growing trade of this new class of air filter media.