Filtration efficiency of makeshift material masks vs. surgical/procedure masks and/or filtering facepiece respirators: a narrative review

Background and Objective: Face mask requirements continue to evolve on local, state, and federal levels. While surgical masks and high-filtration respirators provide higher levels of protection than makeshift material (e.g., cloth) masks, it is difficult to quantitatively compare reported filtration efficiency across different studies due to the variability in study methodologies. The objective of this review is to compare filtration efficiency of homemade face masks constructed from materials readily available within a common household to surgical/procedure masks and/or filtering facepiece respirator (FFR) controls. This analysis will provide researchers an overview of the current literature on mask filtration efficiency and underscore methodological limitations to inform future research efforts. Methods: PubMed was searched for all English language articles with no timeframe limitations related to filtration efficiency of makeshift material masks compared to surgical/procedure masks and/or FFRs as of October 8, 2021. Studies were reviewed to determine average filtration efficiencies of makeshift material masks compared to those of surgical/procedure mask and/or FFRs controls, from which the data were stratified by mask or respirator type (i.e., makeshift material, surgical/procedure, FFR), experimental setup (i.e., manikin, testing rig, filter tester, test subjects), and test aerosol. The data for makeshift materials were further organized by material composition and number of layers. Key Content and Findings: Filtration efficiency is generally the highest across all experimental categories in FFRs (45.68-100%), as expected, followed by surgical/procedure masks (12.4-100%) and then makeshift materials (0.433-100%). However, it is difficult to make any lateral comparisons given the variability in study methodologies and various data reporting limitations. Conclusions: Future research efforts can aim to use officially recognized methods to reduce variability in study protocols, improve on data reporting by providing clear, quantifiable results, and provide more comprehensive reporting of study parameters (e.g., flow rate, face velocity, particle type and size, mask layers, and composition). These measures will help improve readability and direct comparisons across different studies.