Performance Comparison among KN95-Certified Face Masks by Classical Techniques and Innovative Test

Featured Application: A potential application of the methodologies employed within the present work may be related to an easier and cheaper characterization of new materials developed for filtering purposes (specifically concerning the development of face masks for health issues). The possibility to employ a fast characterization technique as an official process to determine the filtering efficiency would both improve the solidity of the characterization method as well as lighten the bureaucratic burden which likely restricts the materials’ supply in shortage periods due to the long validation tests required for their trade. During the pandemic, the provision of Personal Protective Equipment (PPE) (e.g., face masks) to specialized personnel and general population represented a critical point to prevent virus spread; in addition, a huge variety of new manufacturers and products entered the market, widening the time required to test and validate the equipment’s performances according to the current regulations. In this study, we employ a simple method recently developed in our laboratory, to discriminate the filtering capability of a set of KN95-certified face masks from different producers. The method is based on a methylene blue (MB) solution which is sprayed towards a pneumatic lung simulator, connected to a dummy head dressed in different types of masks. The amounts of MB droplets passing through the tested devices are collected by a cotton pad and analyzed through UV-Vis Diffuse Reflectance. In the framework of interdisciplinary collaborations between the University and the Hospital, additional characterization techniques were performed including light optical and scanning electron microscopy morphological characterization, pressure decay, and bacterial filtration efficiency (BFE). All masks were compared to a reference one, considered the gold standard for filtering performances.