Influence of microstructure and physical characteristics in the performance of non-professional masks sold in São Paulo.

OBJECTIVES:This study evaluates the performance of eight non-professional face masks sold in São Paulo, Brazil, to prevent aerial transmission of the SARS-CoV-2. STUDY DESIGN:This was a case report with comparative testing. METHODS:The masks manufactured with different materials and designs were quantified according to their performance to prevent COVID-19 using two indicators: filtration efficiency (FE) and differential pressure. The fabric grammage and microscopy of the layers were analyzed to understand their influence on the performance indicators. RESULTS:The results show no correlation between grammage in the FE and increasing grammage can compromise breathability indicator. Masks manufactured with cotton widely commercialized during the pandemic have non-uniformized results in FE indicators. CONCLUSIONS:There was no evidence between grammage and the number of layers in the FE indicator. The results pointed out that the layer's composition and the microstructure are the best way to evaluate the performance of non-professional masks used to prevent the aerial transmission of the SARS-CoV-2.